Metal matrix composites, and methods for making the same

ABSTRACT

A holder comprising an insert for reinforcing a metal matrix composite article and methods of making the same. In another aspect, the present invention provides metal matrix composite articles reinforced with an insert(s) and methods of making the same. Useful metal matrix composite articles comprising the inserts include brake calipers.

[0001] This application claims priority to U.S. provisional applicationhaving Serial No. 60/404,729, filed Aug. 20, 2002, the disclosure ofwhich is incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to metal matrix composite insertholder and metal matrix composite articles made using metal matrixcomposite insert holders.

DESCRIPTION OF RELATED ART

[0003] Reinforcement of metal matrices with ceramics is known in the art(see, e.g., U.S. Pat. Nos. 4,705,093 (Ogino), 4,852,630 (Hamajima etal.), 4,932,099 (Corwin et al.), 5,199,481 (Corwin et al.), 5,234,080(Pantale), and 5,394,930 (Kennerknecht), Great Britain Pat. Doc. Nos.2,182,970 A and B, published May 28, 1987 and Sep. 14, 1988,respectively, and PCT applications having publication nos. WO 02/26658,WO 02/27048, and WO 02/27049, published Apr. 4, 2002). Examples ofceramic materials used for reinforcement include particles,discontinuous fibers (including whiskers) and continuous fibers, as wellas ceramic pre-forms.

[0004] Typically, ceramic material is incorporated into a metal toprovide metal matrix composites (MMC) having improved mechanicalproperties compared to the article made of the metal without the ceramicmaterial. For example, conventional brake calipers for motorizedvehicles (e.g., cars and trucks) are typically made of cast iron. Toreduce the overall weight of the vehicle, as well as in particularunsprung weight such as brake calipers, there is a desire to use lighterweight parts and/or materials. One technique for aiding in the design ofMMCs, including placement of the ceramic oxide material and minimizingthe amount of ceramic oxide material needed for the particularapplication, is finite element analysis.

[0005] A brake caliper made of cast aluminum would be about 50% byweight lighter than the same (i.e., the same size and configuration)caliper made of cast iron. The mechanical properties of cast aluminumand cast iron are not the same (e.g., the Young's modulus of cast ironis about 100-170 GPa, while for cast aluminum it is about 70-75 GPa; theyield strength of cast iron is 300-700 MPa, while for cast aluminum itis 200-3000 MPa). Hence, for a given size and shape, a brake calipermade from cast aluminum has significantly lower mechanical propertiessuch as bending stiffness and yield strength than the cast iron caliper.Typically, the mechanical properties of such an aluminum brake caliperare unacceptably low as compared to a cast iron brake caliper. A brakecaliper made of an aluminum metal matrix composite material (e.g.,aluminum reinforced with ceramic fibers) that has the same configurationand at least the same (or better) mechanical properties, such as bendingstiffness and yield strength, as a cast iron brake caliper is desirable.

[0006] One consideration for some MMC articles is the need forpost-formation machining (e.g., adding holes or threads, or otherwisecutting away material to provide a desired shape) or other processing(e.g., welding two MMC articles together to make a complex shaped part).Many conventional MMCs typically contain enough ceramic reinforcementmaterial to make machining or welding impractical or even impossible. Itis desirable, however, to produce “net-shaped” articles that requirelittle, if any, post-formation machining or processing. Techniques formaking “net-shaped” articles are known in the art (see, e.g., U.S. Pat.Nos. 5,234,045 (Cisko) and 5,887,684 (Döll et al.)). In addition, oralternatively, to the extent feasible, the ceramic reinforcement may bereduced or not placed in areas where it may interfere with machining orother processing such as welding.

[0007] Another consideration in designing and making MMCs is the cost ofthe ceramic reinforcement material. The mechanical properties ofcontinuous polycrystalline alpha-alumina fibers such as that marketed bythe 3M Company, St. Paul, Minn., under the trade designation “NEXTEL610”, are high compared to low density metals such as aluminum. Inaddition, the cost of ceramic oxide materials such as thepolycrystalline alpha-alumina fibers, is substantially more than metalssuch as aluminum. Hence, it is desirable to minimize the amount ofceramic oxide material used, and to optimize the placement of theceramic oxide materials in order to maximize the properties imparted bythe ceramic oxide materials. Further, it is desirable to provide theceramic reinforcement material in a package or form that can berelatively easily used to make a metal matrix composite articletherefrom.

[0008] PCT applications having publication nos. WO 02/26658, WO02/27048, and WO 02/27049, published Apr. 4, 2002) include descriptionsof embodiments that address the need for ceramic reinforcement materialin a package or form that can be relatively easily used to make a metalmatrix composite article therefrom. These applications also includediscussions of positioning the continuous ceramic fibers used forreinforcement within a mold during the formation of a metal matrixcomposite article (e.g. a brake caliper).

[0009] While techniques for positioning reinforcing fibers is metalmatrix composites are known in the art additional techniques are alsodesirable.

SUMMARY OF THE INVENTION

[0010] In one aspect, the present invention provides insert holders forholding inserts (e.g., metal comprising reinforcement inserts (e.g.,metal matrix composite inserts) and/or ceramic comprising reinforcementinserts) for reinforcing a metal matrix composite article and methods ofmaking the same.

[0011] In one embodiment, the present invention provides a first article(e.g., article for reinforcing a metal matrix composite article)comprising:

[0012] an insert holder including at least one portion for securing atleast one insert, the insert holder comprises a first metal selectedfrom the group consisting of aluminum, alloys thereof (e.g., a 200, 300,400, 700, and/or 6000 series (in some embodiments, preferably a 6000series) aluminum alloy)), and combinations thereof, the insert holderhaving an outer surface, and a second metal on the outer surface of thefirst metal having a positive Gibbs oxidation free energy above at least200° C., the second metal having a thickness of at least 8 micrometers(in some embodiments, preferably 10 micrometers, 12 micrometers, or even15 micrometers; more preferably, in the range from 12 to 15micrometers); and

[0013] at least one reinforcement insert (e.g., a metal comprisingreinforcement insert(s) (e.g., a metal matrix composite insert(s))and/or a ceramic comprising reinforcement insert(s)) secured in the atleast one portion for securing at least one insert. Optionally, thefirst metal matrix composite article further comprises a metal (e.g.,Ni) between the second metal and the outer surface of the first metal.Optionally, an insert holder further comprises one or more additional(e.g., a second, third, fourth, fifth, sixth, etc.) portions forsecuring an insert and, correspondingly one or more additional (e.g., asecond, third, fourth, fifth, sixth, etc.) inserts (e.g., a metalcomprising reinforcement insert(s) (e.g., a metal matrix compositeinsert(s)) and/or a ceramic comprising reinforcement insert(s))positioned in the additional portion(s) for securing insert(s).Optionally, an insert holder further comprises one or more (e.g., afirst, second, third, fourth, fifth, sixth, etc.) correspondingly one ormore additional inserts (e.g., a metal comprising reinforcementinsert(s) (e.g., a metal matrix composite insert(s)).

[0014] In some embodiments, the present invention provides a preferred,second article comprising:

[0015] an insert holder including at least one portion for securing atleast one insert, the insert holder comprises a first metal selectedfrom the group consisting of aluminum, alloys thereof (e.g., a 200, 300,400, 700, and/or 6000 series (in some embodiments, preferably a 6000series) aluminum alloy)), and combinations thereof, the insert holderhaving an outer surface, and a second metal on the outer surface of thefirst metal, the second metal having a positive Gibbs oxidation freeenergy above at least 200° C.; and

[0016] at least one metal matrix composite insert secured in the atleast one portion for securing at least one insert, wherein at least oneof such inserts comprises:

[0017] substantially continuous ceramic oxide fibers and third metalselected from the group consisting of aluminum, alloys thereof (e.g., a200, 300, 400, 700, and/or 6000 series (in some embodiments, preferablya 200 series) aluminum alloy)), and combinations thereof, wherein thethird metal secures the substantially continuous ceramic oxide fibers inplace, and wherein the third metal extends along at least a portion ofthe length of the substantially continuous ceramic oxide fibers, thethird metal having an outer surface; and

[0018] a fourth metal on the outer surface of the third metal, thefourth metal having a positive Gibbs oxidation free energy above atleast 200° C., and the fourth metal having a thickness of at least 8micrometers (in some embodiments, preferably 10 micrometers, 12micrometers, or even 15 micrometers; more preferably, in the range from12 to 15 micrometers).

[0019] Optionally, the second metal matrix composite article furthercomprises a metal (e.g., Ni) between the second metal and the outersurface of the first metal. In addition, or alternatively, optionally,the third metal matrix composite article further comprises a metal(e.g., Ni) between the fourth metal and the outer surface of the thirdmetal. Optionally, an insert holder further comprises one or moreadditional (e.g., a second, third, fourth, fifth, sixth, etc.) portionsfor securing an insert and, correspondingly one or more additional(e.g., a second, third, fourth, fifth, sixth, etc.) inserts (e.g., ametal comprising reinforcement insert(s) (e.g., a metal matrix compositeinsert(s)) and/or a ceramic comprising reinforcement insert(s))positioned in the additional portion(s) for securing insert(s).

[0020] In some embodiments, the present invention provides a preferred,third article comprising:

[0021] an insert holder including at least one portion for securing atleast one insert, the insert holder comprises a first metal selectedfrom the group consisting of aluminum, alloys thereof (e.g., a 200, 300,400, 700, and/or 6000 series (in some embodiments, preferably a 6000series) aluminum alloy)), and combinations thereof; and

[0022] at least one metal matrix composite insert positioned in the atleast one portion for securing at least one insert, the insertcomprising substantially continuous ceramic oxide fibers and secondmetal selected from the group consisting of aluminum, alloys thereof(e.g., a 200, 300, 400, 700, and/or 6000 series (in some embodiments,preferably a 200 series) aluminum alloy)), and combinations thereof,wherein the second metal secures the substantially continuous ceramicoxide fibers in place, and wherein the second metal extends along atleast a portion of the length of the substantially continuous ceramicoxide fibers,

[0023] the insert holder with the at least one insert secured in the atleast one portion for securing at least one insert collectively havingan outer surface, and a third metal on the outer surface, the thirdmetal having a positive Gibbs oxidation free energy above at least 200°C., and the third metal having a thickness of at least 8 micrometers (insome embodiments, preferably 10 micrometers, 12 micrometers, or even 15micrometers; more preferably, in the range from 12 to 15 micrometers).

[0024] Optionally, the third metal matrix composite article furthercomprises a metal (e.g., Ni) between the third metal and the outersurface. Optionally, an insert holder further comprises one or moreadditional (e.g., a second, third, fourth, fifth, sixth, etc.) portionsfor securing an insert and, correspondingly one or more additional(e.g., a second, third, fourth, fifth, sixth, etc.) inserts (e.g., ametal comprising reinforcement insert(s) (e.g., a metal matrix compositeinsert(s)) and/or a ceramic comprising reinforcement insert(s))positioned in the additional portion(s) for securing insert(s).

[0025] In some embodiments, the present invention provides a preferred,fourth metal matrix composite article comprising a first metal (e.g.,aluminum, alloys thereof (e.g., a 200, 300, 400, 700, and/or 6000 series(in some embodiments, preferably a 300 or 400 series) aluminum alloy),and combinations thereof) and an insert holder including at least oneportion for securing at least one insert, wherein the insert holdercomprises:

[0026] a second metal selected from the group consisting of aluminum,alloys thereof (e.g., a 200, 300, 400, 700, and/or 6000 series (in someembodiments, preferably a 6000 series) aluminum alloy), and combinationsthereof); and

[0027] at least one reinforcement insert (e.g., a metal comprisingreinforcement insert(s) (e.g., a metal matrix composite insert(s))and/or a ceramic comprising reinforcement insert(s)) secured in the atleast one portion for securing at least one insert,

[0028] wherein there is an interface layer between the first metal andthe insert holder, and wherein there is an interface layer peak bondstrength value between the first metal and the insert holder of at least100 MPa (in some embodiments, preferably at least 125 MPa, at least 150MPa, at least 175, or even at least 180 MPa).

[0029] Optionally, the insert holder(s) further comprises one or moreadditional (e.g., a second, third, fourth, fifth, sixth, etc.) portionsfor securing an insert and, correspondingly one or more additional(e.g., a second, third, fourth, fifth, sixth, etc.) inserts (e.g., ametal comprising reinforcement insert(s) (e.g., a metal matrix compositeinsert(s)) and/or a ceramic comprising reinforcement insert(s))positioned in the additional portion(s) for securing insert(s).

[0030] In another aspect with regard to the fourth preferred metalmatrix composite article according to the present invention, in someembodiments preferably, the interface layer is free of oxygen. Inanother aspect, the interface layer may include an average amount of ametal having a positive Gibbs oxidation free energy above at least 200°C. (e.g., silver, gold, alloys thereof, and combinations thereof), andwherein the average amount of such metal is (e.g., at least 15, 20, 25,30, 35, 40, 45, or even, 50 percent by weight) higher in the interfacelayer than in the first metal. In another aspect, the interface layermay include an average amount of Ag and Ni (e.g., at least 15, 20, 25,30, 35, 40, 45, or even, 50 percent by weight of each Ag and Ni) higherthan that present in the first metal. In another aspect, the first andsecond metals may each have a melting point, wherein the melting pointof the second metal is at least 10° C., 15° C., 20° C., 25° C., 30° C,35° C., 40° C., 45° C., or even 50° C. higher than the melting point ofthe first metal. In another aspect, the first metal and second metalsmay be different (e.g., aluminum and an aluminum alloy, or differentaluminum alloys).

[0031] In some embodiments, the present invention provides a preferredfifth metal matrix composite article comprising a first metal (e.g.,aluminum, alloys thereof (e.g., a 200, 300, 400, 700, and/or 6000 series(in some embodiments, preferably a 300 or 400 series) aluminum alloy),and/or combinations thereof) and an insert holder including at least oneportion for securing at least one insert, wherein the insert holdercomprises:

[0032] a second metal selected from the group consisting of aluminum,alloys thereof (e.g., a 200, 300, 400, 700, and/or 6000 series (in someembodiments, preferably a 6000 series) aluminum alloy), and combinationsthereof); and

[0033] at least one metal matrix composite insert secured in the atleast one portion for securing at least one insert, the metal matrixcomposite insert comprising:

[0034] substantially continuous ceramic oxide fibers and third metalselected from the group consisting of aluminum, alloys thereof (e.g., a200, 300, 400, 700, and/or 6000 series (in some embodiments, preferablya 200 series) aluminum alloy), and combinations thereof), wherein thethird metal secures the substantially continuous ceramic oxide fibers inplace, and wherein the third metal extends along at least a portion ofthe length of the substantially continuous ceramic oxide fibers,

[0035] wherein there is an interface layer between the first metal andthe insert holder, wherein the interface layer is free of oxygen,wherein the interface layer includes an average amount of a fourth metalhaving a positive Gibbs oxidation free energy above at least 200° C.,and wherein the average amount of the fourth metal in the interfacelayer is higher in the interface layer than that present in the firstmetal. In some embodiments, preferably the average amount of the fourthmetal is at least 15, 20, 25, 20, 35, 40, 45, or even, 50 percent byweight higher in the interface layer than in the first metal. In anotheraspect, the interface layer may also include an average amount of Ni(e.g., at least 15, 20, 25, 20, 35, 40, 45, or even, 50 percent byweight of each Ag and Ni) higher than that present in the first metal.In another aspect, the first and second metals may each have a meltingpoint, wherein the melting point of the second metal is at least 10° C.,15° C., 20° C., 25° C., 30° C., 35° C., 40° C., 45° C., or even 50° C.higher than the melting point of the first metal. In another aspect, thefirst metal and second metals may be different (e.g., aluminum and analuminum alloy, or different aluminum alloys).

[0036] Optionally, the insert holder(s) further comprises one or moreadditional (e.g., a second, third, fourth, fifth, sixth, etc.) portionsfor securing an insert and, correspondingly one or more additional(e.g., a second, third, fourth, fifth, sixth, etc.) inserts (e.g., ametal comprising reinforcement insert(s) (e.g., a metal matrix compositeinsert(s)) and/or a ceramic comprising reinforcement insert(s))positioned in the additional portion(s) for securing insert(s).

[0037] In another aspect, the present invention provides a method ofmaking a metal matrix composite article, the method comprising:

[0038] positioning an insert holder (e.g., a first, second, third,fourth, or fifth article according to the present invention) thatincludes an insert(s) (e.g., a metal comprising reinforcement insert(s)(e.g., a metal matrix composite insert(s)) and/or a ceramic comprisingreinforcement insert(s));

[0039] providing molten metal selected from the group consisting ofaluminum, alloys thereof (e.g., a 200, 300, 400, 700, and/or 6000 series(in some embodiments, preferably a 300 or 400 series) aluminum alloy),and combinations thereof) into the mold; and

[0040] cooling the molten metal to provide a metal matrix compositearticle. Surprisingly, embodiments of the present invention can be usedto make metal matrix composite articles wherein the molten metal in themold to be in the molten state for less than 75 seconds (in someembodiments, preferably less than 60 seconds). By contrast, conventionalmethods tend to require the molten metal in the mold is in the moltenstate for 200 seconds or more. Although not wanting to be bound bytheory, it is believed that the presence of the metal having a positiveGibbs oxidation free energy above at least 200° C. enables formation ofa bond between the holder and/or insert, as applicable, and the metal ofthe metal matrix composite article (in some embodiments, preferablywithout an oxide layer at the interface) and hence does not require anextended period of heating of the interface by molten aluminum oraluminum alloy, as applicable to attempt to break up the oxide layer toachieve metallurgical bonding.

[0041] In this application:

[0042] “a positive Gibbs oxidation free energy above at least 200° C.”refers to the quantity ΔG⁰ _(rxn)=ΔH⁰ _(rxn)−TΔS⁰ _(rxn) where ΔH⁰_(rxn) is the enthalpy of the oxidation reaction in kJ/mol, T is thetemperature in degrees Kelvin, and ΔS⁰ _(rxn) is the entropy of theoxidation reaction (in kJ/mol° K.) remaining positive for temperaturesgreater than 200° C. (473° K.);

[0043] “peak bond strength value” refers to the peak bond strength valueas determined by the “Peak Bond Strength” test described below;

[0044] “free of oxygen” means no visibly discernable continuous oxidelayer at the interface when viewed at 250× with optical microscope asdescribed in the “Oxygen Layer Test” below; and

[0045] “substantially continuous ceramic oxide fibers” refers to ceramicoxide fibers having lengths of at least 5 cm.

[0046] First, second, third, fourth, or fifth articles according to thepresent invention are useful, for example, to provide reinforcementmaterial in metal matrix composite articles. One advantage of someembodiments of the present invention allow for an existing article madeof (original) metal (e.g., cast iron) to be redesigned to be made fromanother metal (e.g., aluminum) reinforced with substantially continuousfibers such that the latter (i.e., the metal matrix composite version ofthe article) has certain desired properties (e.g., Young's modulus,yield strength, and ductility) at least equal to that required for theuse of the original article made from the original metal. Optionally,the article may be redesigned to have the same physical dimensions asthe original article.

[0047] Examples of fourth and fifth metal matrix articles according tothe present invention include brake calipers and high speed mechanicalarms for industrial machinery.

BRIEF DESCRIPTION OF THE DRAWING

[0048]FIG. 1 is a perspective view of an exemplary article according tothe present invention useful for making a fourth or fifth metal matrixcomposite article according to the present invention.

[0049]FIG. 1A is a cutaway view of a portion of FIG. 1.

[0050]FIGS. 2 and 3 are perspective views of an exemplary insert used inan article according to the present invention.

[0051]FIG. 4 is a perspective view of a ceramic fiber ribbon used tomake an exemplary ceramic comprising insert used in an article accordingto the present invention.

[0052]FIG. 5 is a perspective view of an apparatus for making anexemplary ceramic comprising insert used in an article according to thepresent invention.

[0053]FIG. 6 is a perspective view of a brake caliper with an insertholder according to the present invention and exemplary inserts.

[0054]FIG. 7 is a plan view of an exemplary brake caliper according tothe present invention.

[0055]FIGS. 8A, 8B, and 8C are plan views of an exemplary insert holderaccording to the present invention.

[0056]FIG. 9 is a schematic of the compressive shear test equipment usedto determine the peak bond strength value between an insert and themetal of a metal matrix composite article according to the presentinvention made using an insert holder according to the presentinvention.

[0057]FIG. 10 is an optical photomicrograph of a polished cross-sectionof an Example 3 metal matrix composite article of copending applicationhaving U.S. Ser. No. 60/404,672, filed Aug. 20, 2002, the disclosure ofwhich is incorporated herein by reference.

[0058]FIG. 11 is an optical photomicrograph of a polished cross-sectionof a Comparative Example H metal matrix composite article of copendingapplication having U.S. Ser. No. 60/404,672, filed Aug. 20, 2002, thedisclosure of which is incorporated herein by reference.

[0059]FIG. 12 is a schematic of a die cavity used to make the metalmatrix composite article of Example 2 made using the inserts describedin Example 2.

DETAILED DESCRIPTION

[0060] First, second, third, fourth, and fifth articles according to thepresent invention may be, and typically are, designed for the particularapplication to achieve an optimal, or at least acceptable balance of,desired properties, low cost, and ease of manufacture.

[0061] Typically, First, second, third, fourth, and fifth articlesaccording to the present invention are designed for a specificapplication and/or to have certain properties and/or features. Forexample, an existing article made of one metal (e.g., cast iron) isselected to be redesigned to be made from another metal (e.g., aluminum)reinforced with metal and/or ceramic comprising inserts such that thelatter (i.e., the metal matrix composite version of the article) hascertain desired properties (e.g., Young's modulus, yield strength, andductility) at least equal to that required for the use of the originalarticle made from the first metal. Optionally, the article may beredesigned to have the same physical dimensions as the original article.

[0062] The desired metal matrix composite article configuration, desiredproperties, possible metals and ceramic oxide material from which it maybe desirable for it to be made of, as well as relevant properties ofthose materials are collected and used to provide possible suitableconstructions. In some embodiments, a preferred method for generatingpossible constructions is the use of finite element analysis (FEA),including the use of FEA software run with the aid of a conventionalcomputer system (including the use of a central processing unit (CPU)and input and output devices). Suitable FEA software is commerciallyavailable, including that marketed by Ansys, Inc., Canonsburg, Pa. underthe trade designation “ANSYS”. FEA assists in modeling the articlemathematically and identifying regions where placement of the ceramicoxide fibers, for example, would provide the desired property levels. Itis typically necessary to run several iterations of FEA to obtain a morepreferred design. Such results can be used to design and prepare, forexample, the holder(s) and insert(s) used to make metal matrix compositearticles In some embodiments, the holder may further comprises one ofmore (e.g., two, three, four, five, etc.) apertures. Such apertures canbe helpful, for example, during casting by allowing molten metal to flowthrough portions of the holder.

[0063] The holder can facilitate the position of reinforcement insertswhen making fourth and fifth metal matrix articles according to thepresent invention. An exemplary holder with inserts positioned thereinis shown in FIGS. 1 and 1A. Referring to FIG. 1, article according tothe present invention 10 comprises holder 11 portions 12A, 12B, 12C, and12D for securing inserts 13A, 13B, and 13C. Referring to FIG. 1A, holder11 comprises aluminum and/or alloy(s) thereof 14, outer surface 15,metal having a positive Gibbs oxidation free energy above at least 200°C. 17, and optional additional metal (e.g., Ni) 16 and outer surface 18of optional metal 16.

[0064] The holder comprises aluminum, alloys thereof (e.g., a 200, 300,400, 700, and/or 6000 series (in some embodiments, preferably a 6000series) aluminum alloy)), more typically an aluminum and/or alloy(s)thereof (e.g., a 200, 300, 400, 700, or 6000 series), and combinationsthereof.

[0065] Suitable aluminum and aluminum alloys are commercially available,for example, from Alcoa of Pittsburgh, Pa. and Belmont Metals, New York,N.Y. In some embodiments, examples of preferred aluminum alloys includealloys comprising at least 98 percent by weight Al, aluminum alloycomprises at least 1.5 percent by weight Cu (e.g., aluminum alloyscomprising Cu in the range from 1.5 to 2.5, preferably, 1.8 to 2.2,percent by weight Cu, based on the total weight of the alloy), and 200(e.g., A201.1 aluminum alloy, 201.2 aluminum alloy, A206.0 aluminumalloy, and 224.2 aluminum alloy), 300 (e.g., A319.1 aluminum alloy,354.1 aluminum alloy, 355.2 aluminum alloy, and A356.1 aluminum alloy),400 (e.g., 443.2 aluminum alloy and 444.2 aluminum alloy), 700 (e.g.,713 aluminum alloy), and 6000 (e.g., 6061 aluminum alloy) seriesaluminum alloys. In some embodiments, the holders preferably comprises a300, 400, 6000 series aluminum alloy e.g., A319.1 aluminum alloy, 354.1aluminum alloy, 355.2 aluminum alloy, A356.1 aluminum alloy, 443.2aluminum alloy, 444.2 aluminum alloy, and 6061 aluminum alloy).

[0066] The holder can be made using conventional techniques, such ascutting a sheet of aluminum and/or alloy(s) thereof and bending the cutsheet to obtain the desired holder configuration. Optionally, the sheetcan comprise, for example, a combination of aluminum and an alloythereof or two or more different aluminum alloys, etc. For example, thesheet may comprise a sheet of aluminum laminated to, co-cast with, etc.a sheet of aluminum alloy.

[0067] Optionally, the holder further comprises, for example, ceramicoxide fibers to aid in reinforcing the holder. For example, if thefibers can be incorporated into a sheet during its formation. The fibersmay even be selectively located in the sheet such that after the sheetis cut and bent into the desired configuration, the fibers located, forexample, in selected portions of the holder. Examples of suitable fibersinclude those described below for making inserts.

[0068] Although thicknesses of the metal having a positive Gibbsoxidation free energy above at least 200° C. outside of specified valuesmay also be useful, if the thickness is too low, the coatings tend todiffuse when the holder is preheated and consequently may not protectthe interface from oxidation or otherwise aid in reducing oxidation atthe interface, while excess thicknesses tend to interfere with theestablishment of a desirable bond strength between the metal of theholder and the metal of the metal matrix composite article. Techniquesfor depositing metal having a positive Gibbs oxidation free energy aboveat least 200° C. are known in the art and include electroplating.

[0069] Typically, thicknesses of the optional Ni are greater than about1 micrometer, more typically greater than 2 micrometers, or even greaterthan 3 micrometers. In another aspect, typically thicknesses of suchmetal are less than about 10 micrometers, more typically less than about5 micrometers. Although thicknesses outside of these values may also beuseful, if the thickness is too low, the coatings tend not be as usefulin aiding the adhesion of the metal having a positive Gibbs oxidationfree energy above at least 200° C. to the holder, while excessthicknesses tend to interfere with the establishment of a desirable bondstrength between the metal of the holder and the metal of the metalmatrix composite. In some embodiments, the Ni is deposited viaelectroless deposition.

[0070] The resulting holder can be further processed (e.g., sand blastedand/or surface ground (e.g., with a vertical spindle diamond grinder),for example to remove or reduce oxidation on the surface of the holder.The holder may also be cut as needed to provide a desired shape(including being cut with a water jet). Next, the holder is coated withmetal having a positive Gibbs oxidation free energy above at least 200°C. Optionally, a metal such as Ni is coated onto the holder prior tocoating the metal having a positive Gibbs oxidation free energy above atleast 200° C. The use of the Ni tends to aid in the adhesion of metalsuch as Ag to the holder.

[0071] Examples of reinforcement inserts for practicing embodiments ofthe present invention include metal comprising reinforcement inserts(e.g., a metal matrix composite inserts) and ceramic comprisingreinforcement inserts.

[0072] In some embodiments, a preferred metal matrix composite insert,comprises metal (e.g. aluminum and/or an alloy(s) thereof) andsubstantially continuous ceramic oxide fibers. In some embodiments, apreferred ceramic comprising insert comprises ceramic (typically porousceramic (e.g., alpha alumina)) and substantially continuous ceramicoxide fibers. Referring to FIG. 2, exemplary insert 20 comprisessubstantially continuous (as shown, longitudinally aligned) ceramicoxide fibers 22, ceramic or metal (e.g., aluminum and/or alloy(s)thereof) 24, metal having a positive Gibbs oxidation free energy aboveat least 200° C. 26 is on outer surface 25, and optionally additionalmetal (e.g., Ni) 28 is positioned between outer surface 25 and metalhaving a positive Gibbs oxidation free energy above at least 200° C. 26,and has outer surface 27 such that metal having a positive Gibbsoxidation free energy above at least 200° C. 26 is on outer surface 27.

[0073] The inserts may comprise more than one groupings (e.g., twogroupings, three groupings, etc.) of substantially continuous ceramicoxide fibers, wherein a grouping of substantially continuous ceramicoxide fibers is spaced apart from another grouping(s) with, for examplemetal or ceramic there between. For example, referring to FIG. 3 insert30 comprises groupings 32A, 32B, and 32C of substantially continuous,substantially continuous ceramic oxide fibers 32 and metal or ceramic34, aluminum and/or alloy(s) thereof 35, outer surface 36, metal havinga positive Gibbs oxidation free energy above at least 200° C. 37, andoptional additional metal (e.g., Ni) 38 and outer surface 39 of optionalmetal 38.

[0074] In some exemplary embodiments of the present invention, thesubstantially continuous ceramic oxide fibers are substantiallylongitudinally aligned such that they are generally parallel to eachother. While the ceramic oxide fibers may be incorporated into the metalmatrix composite inserts as individual fibers, they are more typicallyincorporated into the metal matrix composite inserts as a group offibers in the form of a bundle or tow. Fibers within the bundle or towmay be maintained in a longitudinally aligned (i.e., generally parallel)relationship with one another. When multiple bundles or tows areutilized, the fiber bundles or tows are also maintained in alongitudinally aligned (i.e., generally parallel) relationship with oneanother. In some embodiments, it is preferred that all of the continuousceramic oxide fibers are maintained in an essentially longitudinallyaligned configuration where individual fiber alignment is maintainedwithin ±10°, more preferably ±5°, most preferably ±3°, of their averagelongitudinal axis.

[0075] It is also within the scope of the present invention for theceramic oxide fibers to be curved, as opposed to straight (i.e., do notextend in a planar manner). Hence, for example, the ceramic oxide fibersmay be planar throughout the fiber length, non-planar (i.e., curved)throughout the fiber length, or they may be planar at some portions andnon-planar (i.e., curved) at other portions. In some embodiments, thesubstantially continuous ceramic oxide fibers are maintained in asubstantially non-intersecting, curvilinear arrangement (i.e.,longitudinally aligned) throughout the curved portion of the metalmatrix composite article. In some embodiments, the substantiallycontinuous ceramic oxide fibers are maintained in a substantiallyequidistant relationship with each other throughout the curved portionof the insert.

[0076] It is also within the scope of the present invention for theceramic oxide fibers to be present as two, three, four, or more plies(i.e., a ply is at least one layer of substantially continuous ceramicoxide fibers (in some embodiments, preferably at least one layer of towscomprising the substantially continuous ceramic oxide fibers)). Theplies may be oriented with respect to each other any of a variety ofways. For example, a first ply of substantially continuous ceramic oxidefibers may be positioned between 0° and 90° with respect to second plyof substantially continuous ceramic oxide fibers. In some embodiments,preferred positioning of a ply with respect to another ply(s) for someapplications may be in the range from about 30° to about 60°, or even,for example, in the range from about 40° to about 50°.

[0077] Typically, the substantially continuous ceramic oxide fibers havelengths of at least 10 cm (frequently at least 15 cm, 20 cm, 25 cm, ormore). In some embodiments of the present invention, the substantiallycontinuous ceramic oxide fibers are in the form of tows (i.e., the towscomprise the substantially continuous ceramic oxide fibers). Typically,the substantially continuous ceramic oxide fibers comprising the towhave lengths of at least 10 cm (frequently at least 15 cm, 20 cm, 25 cm,or more).

[0078] The ceramic oxide fibers can include, or even consist essentiallyof, substantially continuous, longitudinally aligned, ceramic oxidefibers, wherein “longitudinally aligned” refers to the generallyparallel alignment of the fibers relative to the length of the fibers.

[0079] In some embodiments, the substantially continuous reinforcingceramic oxide fibers preferably have an average diameter of at leastabout 5 micrometers. In some embodiments, the average fiber diameter isno greater than about 200 micrometers, preferably, no greater than about100 micrometers. For tows of fibers, in some embodiments, the averagefiber diameter is preferably, no greater than about 50 micrometers, morepreferably, no greater than about 25 micrometers. in some embodiments,preferably the substantially continuous ceramic oxide fibers have aYoung's modulus of greater than about 70 GPa, more preferably, at least100 GPa, at least 150 GPa, at least 200 GPa, at least 250 GPa, at least300 GPa, or even at least 350 GPa.

[0080] In some embodiments, preferably the continuous ceramic oxidefibers have an average tensile strength of at least about 1.4 GPa, morepreferably, at least about 1.7 GPa, even more preferably, at least about2.1 GPa, and most preferably, at least about 2.8 GPa, although fiberswith lower average tensile strengths may also be useful, depending onthe particular application.

[0081] Continuous ceramic oxide fibers are available commercially assingle filaments, or grouped together (e.g., as yarns or tows). Yarns ortows may comprise, for example, at least 420 individual fibers per tow,at least 760 individual fibers per tow, at least 2600 individual fibersper tow, or more. Tows are well known in the fiber art and refer to aplurality of (individual) fibers (typically at least 100 fibers, moretypically at least 400 fibers) collected in an aligned untwisted form,whereas yarns imply some degree of twist or rope-like construction.Ceramic oxide fibers, including tows of ceramic oxide fibers, areavailable in a variety of lengths. The fibers may have a cross-sectionalshape that is circular or elliptical.

[0082] Examples of useful ceramic oxide fibers include alpha aluminafibers, aluminosilicate fibers, and aluminoborosilicate fibers. Otheruseful ceramic oxide fibers may be apparent to those skilled in the artafter reviewing the present disclosure.

[0083] Methods for making alumina fibers are known in the art andinclude the method disclosed in U.S. Pat. No. 4,954,462 (Wood et al.),the disclosure of which is incorporated herein by reference. In someembodiments, preferably the alumina fibers are polycrystalline alphaalumina-based fibers and comprise, on a theoretical oxide basis, greaterthan about 99 percent by weight Al₂O₃ and about 0.2-0.5 percent byweight SiO₂, based on the total weight of the alumina fibers. In anotheraspect, in some embodiments, preferable polycrystalline, alphaalumina-based fibers comprise alpha alumina having an average grain sizeof less than 1 micrometer (more preferably, less than 0.5 micrometer).In another aspect, in some embodiments, preferable polycrystalline,alpha alumina-based fibers have an average tensile strength of at least1.6 GPa (preferably, at least 2.1 GPa, more preferably, at least 2.8GPa). Alpha alumina fibers are commercially available, for example,under the trade designation “NEXTEL 610” from the 3M Company of St.Paul, Minn. Another alpha alumina fiber, which comprises about 89percent by weight Al₂O₃, amount 10 percent by weight ZrO₂, and about 1percent by weight Y₂O₃, based on the total weight of the fibers, iscommercially available from the 3M Company under the trade designation“NEXTEL 650”.

[0084] Methods for making aluminosilicate fibers are known in the artand include the method disclosed in U.S. Pat. No. 4,047,965 (Karst etal.), the disclosure of which is incorporated herein by reference. Insome embodiments, preferably the aluminosilicate fibers comprise, on atheoretical oxide basis, in the range from about 67 to about 85 percentby weight Al₂O₃ and in the range from about 33 to about 15 percent byweight SiO₂, based on the total weight of the aluminosilicate fibers. Insome embodiments, preferable aluminosilicate fibers comprise, on atheoretical oxide basis, in the range from about 67 to about 77 percentby weight Al₂O₃ and in the range from about 33 to about 23 percent byweight SiO₂, based on the total weight of the aluminosilicate fibers. Insome embodiments, preferable aluminosilicate fibers comprise, on atheoretical oxide basis, about 85 percent by weight Al₂O₃ and about 15percent by weight SiO₂, based on the total weight of the aluminosilicatefibers. In some embodiments, preferable aluminosilicate fibers comprise,on a theoretical oxide basis, about 73 percent by weight Al₂O₃ and about27 percent by weight SiO₂, based on the total weight of thealuminosilicate fibers. Aluminosilicate fibers are commerciallyavailable, for example, under the trade designations “NEXTEL 440”,“NEXTEL 720”, and “NEXTEL 550” from the 3M Company.

[0085] Methods for making aluminoborosilicate fibers are known in theart and include the method disclosed in U.S. Pat. No. 3,795,524(Sowman), the disclosure of which is incorporated herein by reference.In some embodiments, preferably the aluminoborosilicate fibers comprise,on a theoretical oxide basis: about 35 percent by weight to about 75percent by weight (or even, for example, about 55 percent by weight toabout 75 percent by weight) Al₂O₃; greater than 0 percent by weight (oreven, for example, at least about 15 percent by weight) and less thanabout 50 percent by weight (or, for example, less than about 45 percent,or even less than about 44 percent) SiO₂; and greater than about 5percent by weight (or, for example, less than about 25 percent byweight, less than about 1 percent by weight to about 5 percent byweight, or even less than, about 2 percent by weight to about 20 percentby weight) B₂O₃, based on the total weight of the aluminoborosilicatefibers. Aluminoborosilicate fibers are commercially available, forexample, under the trade designation “NEXTEL 312” from the 3M Company.

[0086] Commercially available substantially continuous ceramic oxidefibers often include an organic sizing material added to the fiberduring their manufacture to provide lubricity and to protect the fiberstrands during handling. It is believed that the sizing tends to reducethe breakage of fibers, reduces static electricity, and reduces theamount of dust during, for example, conversion to a fabric. The sizingcan be removed, for example, by dissolving or burning it away.

[0087] It is also within the scope of the present invention to havecoatings on the ceramic oxide fibers. Coatings may be used, for example,to enhance the wettability of the fibers, to reduce or prevent reactionbetween the fibers and molten metal matrix material. Such coatings andtechniques for providing such coatings are known in the fiber ceramiccomposite, and metal matrix composite art.

[0088] With regard to metal comprising inserts, in some embodiments,metal matrix composite inserts comprise substantially continuous ceramicoxide fibers. Typically, aluminum and/or alloy(s) thereof extends alongat least a portion of the length of the substantially continuous ceramicoxide and secures the ceramic oxide fibers in place.

[0089] Although the aluminum and aluminum alloys used to make, and whichcomprise, metal comprising inserts, including metal matrix compositeinserts, may contain impurities, in some embodiments it may bepreferable to use relatively pure metal (i.e., metal comprising lessthan 0.1 percent by weight, or even less than 0.05 percent by weightimpurities (i.e., less than 0.25 percent 0.1 percent, or even less than0.05 percent by weight of each of Fe, Si, and/or Mg)). Although higherpurity metals tend to be preferred for making higher tensile strengthmaterials, less pure forms of metals are also useful.

[0090] Suitable aluminum and aluminum alloys are commercially available.For example, aluminum is available under the trade designation “SUPERPURE ALUMINUM; 99.99% Al” from Alcoa of Pittsburgh, Pa. Aluminum alloys(e.g., Al-2% by weight Cu (0.03% by weight impurities) can be obtainedfrom Belmont Metals, New York, N.Y. In some embodiments, the insertspreferably comprise a 200 series aluminum alloy (e.g., A20 1.1 aluminumalloy, 201.2 aluminum alloy, A206.0 aluminum alloy, and 224.2 aluminumalloy).

[0091] In some embodiments, first, second and third articles accordingto the present invention that include metal matrix composite insertscomprise, in the region(s) comprising the substantially continuousceramic fibers, in the range from about 30 to about 45 percent (in someembodiments, preferably about 35 to about 45 percent, more preferably,about 35 to about 40 percent) by volume metal and in the range fromabout 70 to about 55 percent (preferably about 65 to about 55 percent,more preferably, about 60 to about 65 percent) by volume of thecontinuous ceramic oxide fibers, based on the total volume of theregion. Further, the region comprising the metal which secures thesubstantially continuous ceramic oxide fibers, typically comprises inthe range from about 20 to about 95 percent (preferably about 60 toabout 90 percent, more preferably, about 80 to about 85 percent) byvolume metal and in the range from about 80 to about 5 percent (in someembodiments, preferably about 60 to about 10 percent, more preferably,about 15 to about 5 percent) by volume metal, based on the total volumeof the region.

[0092] In some embodiments, inserts comprise the substantiallycontinuous ceramic oxide fibers, in the range from about 30 to about 70percent (in some embodiments, preferably about 35 to about 60 percent,or even about 35 to about 45 percent) by volume metal and in the rangefrom about 70 to about 30 percent (in some embodiments, preferably about65 to about 40 percent, or even about 65 to about 55 percent) by volumesubstantially continuous ceramic oxide fibers, based on the total volumeof the insert. In some embodiments, preferably the inserts comprise atleast 50 by volume of the substantially continuous ceramic oxide fibers,based on the total volume of the insert.

[0093] For first, second and third articles according to the presentinvention that include metal matrix composite inserts, the fiber andmetal volume content of the inserts in the substantially continuousfiber region is generally governed by the desired to produce ahomogeneous composite without significant movement of the substantiallycontinuous ceramic oxide fibers during the metal infiltration. If thefiber content is too low, it is more difficult to prevent or minimizemovement of the substantially continuous fibers during the metalinfiltration. In some embodiments, the metal comprising the insert ispreferably selected such that the matrix material does not significantlyreact chemically with the ceramic oxide material, (i.e., is relativelychemically inert with respect to the metallic, refractory material),particularly the substantially continuous ceramic oxide fibers, forexample, to eliminate the need to provide a protective coating on thefiber exterior.

[0094] Metal matrix composite inserts can be made, for example, bywinding a plurality of continuous ceramic oxide fibers (in someembodiments, preferably grouped together (e.g., as yarns or tows)) ontoa mandrel having the desired dimension and shape for the intended metalinsert design. In some embodiments, preferably the fibers being woundare sized. Exemplary sizes include water (in some embodiments,preferably deionized water), wax (e.g., paraffin), and polyvinyl alcohol(PVA). If the sizing is water, the fiber is typically wound onto themandrel. After winding is completed, the mandrel is removed from thewinder and then placed in a refrigerated cooler until the wound fiberfreezes. The frozen, wound fiber can be cut as needed. For example, ifthe fiber is wound around a mandrel made up of four contiguous plates,the rectangular plates can be removed to provide a frozen, fiberpreform. The preform can be cut into pieces to provide small preforms.Typically the sizing is removed before it is used to form a metal matrixcomposite insert. The sizing can removed, for example, by placing theformed fiber into a die (in some embodiments, preferably graphite), andthen heating the die. The die is used to make the metal matrix compositeinsert.

[0095] To form the metal matrix composite insert, after the sizing isremoved, if present, a die is placed in a can, typically a stainlesssteel can, preferably open only at one end. The interior of the can insome embodiments is preferably coated with boron nitride or a similarmaterial to protect, minimize reaction between the aluminum/aluminumalloy and the can during the subsequent casting, and/or facilitaterelease of the metal matrix composite article from the mold. The canwith the die within is placed inside the pressure vessel of a pressurecasting machine. Subsequently, aluminum and/or aluminum alloy (e.g.pieces of aluminum and/or an aluminum alloy cut from an ingot) is placedon top of the can. The pressure vessel is then evacuated of air andheated above the melting point of the aluminum/aluminum alloy (typicallyabout 80° C. to about 120° C. above the liquidus temperature). Uponreaching the desired temperature, the heater is turned off and thepressure vessel is then pressurized with typically argon (or a similarinert gas) to a pressure of about 8.5 to about 9.5 MPa, forcing themolten aluminum/aluminum alloy to infiltrate the preform. The pressurein the pressure vessel is allowed to decay slowly as the temperaturefalls. When the article solidifies (i.e., its temperature drops belowabout 500° C.), chamber is vented, and the cast metal matrix compositearticle(s) (e.g., insert(s)) is removed from the die(s), and thenallowed to further cool in air.

[0096] Metal matrix composite articles (e.g., insert) can also be made,for example, by other techniques known in the art, including squeezecasting. For squeeze casting, for example, the formed ceramic oxidefiber can be placed in a die (e.g., a steel die), any sizing presentburned away, molten aluminum/aluminum alloy introduced into the diecavity, and pressure applied until solidification of the cast article iscomplete. After cooling, the resulting metal matrix composite articleinsert is removed from the die.

[0097] The resulting insert can be further processed (e.g., sand blastedand/or surface ground (e.g., with a vertical spindle diamond grinder),for example to remove or reduce oxidation on the surface of the insert.The insert may also be cut as needed to provide a desired shape(including being cut with a water jet).

[0098] It is within the scope of the present invention to make metalmatrix composites comprising inserts from ceramic comprising inserts,such as those described below.

[0099] In some embodiments, preferably metal matrix composite insertsare coated with metal having a positive Gibbs oxidation free energyabove at least 200° C. A metal such as Ni may be coated onto the metalmatrix composite article insert prior to coating the metal having apositive Gibbs oxidation free energy above at least 200° C. The use ofthe Ni tends to aid in the adhesion of metal such as Ag to the insert.

[0100] Although thicknesses of the metal having a positive Gibbsoxidation free energy above at least 200° C. outside of specified valuesmay also be useful, if the thickness is too low, the coatings tend todiffuse when the insert is preheated and consequently may not protectthe interface from oxidation or otherwise aid in reducing oxidation atthe interface, while excess thicknesses tend to interfere with theestablishment of a desirable bond strength between the two metal of theinsert and the metal of the metal matrix composite article.

[0101] Typically, thicknesses of the optional Ni are greater than about1 micrometer, more typically greater than 2 micrometers, or even greaterthan 3 micrometers. In another aspect, typically thicknesses of suchmetal are less than about 10 micrometers, more typically less than about5 micrometers. Although thicknesses out side of these values may also beuseful, if the thickness is too low, the coatings tend not be as usefulin aiding the adhesion of the metal having a positive Gibbs oxidationfree energy above at least 200° C. to the insert, while excessthicknesses tend to interfere with the establishment of a desirable bondstrength between the metal of the insert and the metal of the metalmatrix composite.

[0102] For additional details on embodiments of metal matrix compositeinserts see copending application having U.S. Ser. No. 60/404,672, filedAug. 20, 2002, the disclosure of which is incorporated herein byreference.

[0103] With regard to ceramic comprising inserts, in some embodiments,preferred embodiments include porous ceramic oxide (e.g., calcined orsintered) inserts comprising substantially continuous ceramic oxidefibers. Typically, porous ceramic oxide extends along at least a portionof the length of the substantially continuous ceramic oxide and securesthe ceramic oxide fibers in place. In some embodiments, thesubstantially continuous ceramic oxide fibers have a first, Young'smodulus, and ceramic oxide material comprising the ceramic preform has asecond Young's modulus, wherein the first Young's modulus is greaterthan the second Young's modulus.

[0104] Continuous reinforcing fibers in the form of woven, knitted, andthe like fiber constructions typically are not capable of achieving thehigher fiber packing densities realized with longitudinally alignedfibers. Thus, metal infiltrated articles based on preforms utilizingwoven, knitted, or the like fiber constructions typically exhibit lowerstrength properties than metal infiltrated articles havinglongitudinally aligned continuous reinforcing fibers and hence are lesspreferred.

[0105] Porous ceramic oxide comprising inserts can be made, for example,by casting a slurry of discontinuous ceramic oxide fibers (includingwhiskers) around the substantially continuous fibers. Typically, thesubstantially continuous fibers are positioned in a cavity (e.g., mold),and the slurry added to the mold. The substantially continuous fibersare positioned within the cavity such that they will be properlypositioned in the resulting ceramic oxide material. The cavity isconfigured to provide the desired shape, although it is also within thescope of the present invention to reshape the resulting ceramic oxidematerial, for example, by machining, to provide the desiredconfiguration of the ceramic oxide comprising insert.

[0106] Suitable discontinuous ceramic oxide fibers (including whiskers)include those made of alumina, including alpha alumina and transitionalaluminas (such as delta alumina), aluminosilicate fibers, andaluminoborosilicate fibers, and methods of making and/or sources of suchmaterials, are known in the art. Discontinuous fibers can be made, forexample, by cutting or chopping continuous fibers (including thesubstantially continuous fibers discussed above). Examples ofcommercially available discontinuous ceramic oxide fibers include thosemarketed under the trade designation “SAFFIL” from J&J Dyson, Widness,UK, “KAOWOOL” from Thermal Ceramics Inc., Augusta, Ga., and “FIBERFRAX”from Unifrax, Niagara Falls, N.Y.

[0107] In some embodiments, the discontinuous fibers have a diameter inthe range from about 1 micrometer to about 20 micrometers, preferably,from about 3 micrometers to about 12 micrometers, and are up to about2.5 cm long, preferably, less than 1.2 cm long, although whiskerstypically have a length in the range from about 6 micrometers to about12 micrometers long.

[0108] Optionally, the slurry may further comprise ceramic oxideparticles such as alumina (including alpha alumina) particles,aluminosilicate particles, and aluminoborosilicate particles. In someembodiments, the preferred average particle size of the particles is inthe range from about 0.05 micrometer to about 50 micrometers. The slurrymay further comprise ceramic oxide bonding materials such as colloidalsilica, colloidal alumina, and the like which can aid in enhancing theintegrity (e.g., by reaction with other components used to make theporous ceramic oxide pre-form to make other phases (e.g., the silica mayreact with alumina to form mullite)).

[0109] Suitable slurries can be formed using techniques known in theart. Typically, slurries are formed by dispersing discontinuous fibersin a liquid medium such as water. To aid in the handling and positioningof the substantially continuous fibers, a fiber insert (e.g., ribbon)can be used. A fiber insert comprises a plurality of the substantiallycontinuous fibers held together with a binder material. Referring toFIG. 4, fiber ribbon 40l comprises substantially continuous,longitudinally aligned, alpha alumina fibers 42 and fugitive bindermaterial 44, which serves to secure fibers 42 (as shown in tows 43) intofiber ribbon 40. Binder material 44 contacts the fibers only to theextent necessary to form fiber ribbon 40, and may not necessarily be incontact with all fibers. For example, internal fibers may not be incontact with the binder material.

[0110] In selecting the binder material for making a fiber insert,consideration is given to adverse effects, if any, the binder materialmay have on the properties of the ceramic oxide comprising insert, aswell as the impact, if any, the binder material may have on the use ofthe ceramic oxide comprising insert (e.g., consideration is given toadverse effects, if any, the binder material may have on the propertiesof a metal matrix composite article made using the ceramic oxidecomprising insert).

[0111] The binder material is used to temporarily bond the substantiallycontinuous fibers together, as well as aid in handling and ultimatelyplacing the fibers in the ceramic oxide comprising insert. In someembodiments, the binder material may preferably be a fugitive material,which preferably bums out at relatively low temperature during thecalcining stage of the pre-form fabrication process leaving no residueor ash. In some embodiments, a preferred fugitive binder material is wax(e.g., paraffin), which can be heated above its melting point, appliedto the fibers, and then solidified to hold the fibers as desired. Insome embodiments, a preferred fugitive binder materials include watersoluble polymers such as polyvinyl alcohol (PVA), polyvinyl pyrrolidone(PVP), and combinations thereof. Other suitable fugitive bindermaterials may include epoxies such as that marketed by Cytec Industries,West Patterson, N.J. (formerly marketed by the 3M Company, St. Paul,Minn., under the trade designation “SP381 SCOTCHPLY ADHESIVE”).

[0112] The ceramic comprising insert is typically designed for a certainpurpose, and as a result, is desired to have certain properties, have acertain configuration, and be made of certain materials. Typically, themold is selected or made to provide the desired shape of the ceramiccomprising insert. Forming a net-shaped, or near net-shaped ceramiccomprising insert, can, for example, minimize or eliminate the need forand cost of subsequent machining or other post-casting processing of theinsert. The cavity is selected or made to have a desired shape for theresulting ceramic comprising insert. Typically, the cavity is made oradapted to hold the substantially continuous fibers in a desiredlocation such that the substantially continuous fibers are properlypositioned in the resulting ceramic comprising insert. Techniques formaking suitable cavities are known to those skilled in the art. Suchcavities may be made of rigid material such as of wood, plastic,graphite, and steel (e.g., stainless steel). To facilitate the removalof liquid from the slurry, one or more apertures can be provided in themold.

[0113] A ceramic comprising insert can be made, for example, bypositioning the substantially continuous fiber in a cavity, introducinga slurry comprising discontinuous ceramic oxide fibers into the cavity,and removing liquid from slurry. Typically, the liquid is removed viaapertures in the cavity. Removal of the liquid through the apertures canbe enhanced by reducing the pressure outside the cavity (e.g., less than1000 mbars, in some embodiments preferably, less than 850 mbars).

[0114] Unless the green insert is dried in the cavity, it is typicallydried after removal from the cavity before calcining or sintering. Insome embodiments, preferably, the green insert is dried to at least onetemperature in the range from about 70° C. to about 100° C., morepreferably, from about 85° C. to about 100° C., and typically mostpreferably, at about 100° C.

[0115] The green insert is typically calcined prior to sintering.Calcining is heating a material to a temperature(s) to eliminate freewater, and in some embodiments, preferably at least about 90 wt-% of anybound volatiles constituents, but without fusion, as opposed tosintering.

[0116] Typical calcining temperatures are in the range from 400° C. toabout 800° C., in some embodiments, preferably from about 600° C. toabout 800° C. Typical sintering temperatures are in the range from 900°C. to about 1150° C., in some embodiments, preferably from about 950° C.to about 1100° C., more preferably from about 950° C. to about 1100° C.

[0117] The drying, calcining, and sintering times may depend, forexample, on the materials involved, as well as the configuration(including size) of the ceramic comprising insert.

[0118] The orientation of the discontinuous fibers with respect to thelength of the substantially continuous fibers may be adjusted by thefabrication process used to make the ceramic comprising insert. Forexample, the positioning apertures in the bottom of the cavity used tohold the slurry to preferentially remove the liquid from the bottom (ortop) of the cavity (as opposed to the sides) may result in the largestdimension of the discontinuous fibers preferentially being moreperpendicular to the length of continuous fibers positioned parallel tothe lengths of the sides of the cavity than parallel. For example,referring to FIG. 5, fiber ribbon 51, which comprises plurality of thesubstantially continuous ceramic oxide fibers 52 held together withbinder material 53, is positioned in cavity 54. The length of continuousfibers 52 is parallel to sides of cavity 54, and perpendicular to bottom56 of cavity 54. Liquid from slurry 57 is removed from via apertures 58,such that the largest dimension of discontinuous fibers preferentiallybeing more perpendicular to the length of continuous fibers 52 thanparallel.

[0119] Preferably, removal of the liquid is aided by reducing pressureoutside of the mold. For example, a fiber insert may be affixed in themold such that it held in the desired location by clips at each end ofthe fiber insert. In one exemplary technique, a screen is placed on oneside of the mold for water removal under reduced pressure (e.g., in someembodiments less than 1000 mbars). The placement of the screen isdetermined by the desired orientation of the discontinuous fibers. Forexample, if it is desired to preferentially align discontinuous fibersto be perpendicular to the lengths of continuous, longitudinally alignedfibers, the screen can be positioned at one of the ends of the fiberlengths, perpendicular to the length of the fibers. The slurry can beadded, for example, by submersing the mold in the slurry, then removingor pumping the slurry from the mold. A reduced pressure can be appliedto the screen side of the mold to draw out the liquid. When the liquidis removed, the discontinuous fibers are preferentially aligned withrespect to the lengths of the substantially continuous fibers.Subsequent pressure may be applied to the fibers to force out morewater, and may also aid in densifying the discontinuous fiber.

[0120] Similarly, for example, positioning apertures or holes in thesides of the cavity used to hold the slurry to preferentially remove theliquid from the sides of the cavity (as opposed to the top and bottom)may result in the largest dimension of the discontinuous fiberspreferentially being more perpendicular to the length of continuousfibers positioned perpendicular to the lengths of the sides of thecavity than parallel.

[0121] For additional details regarding the formation of ceramiccomprising inserts, see, for example, U.S. Pat. No. 5,394,930(Kennerknecht) and Great Britain Pat. Doc. Nos. 2,182,970 A and B.published May 28, 1987 and Sep. 14, 1988, respectively, copending U.S.applications having Ser. Nos. 09/966,946, 09/967,401, and 09/9677,562,filed Sep. 27, 2001, and PCT applications having publication nos. WO02/26658, WO 02/27048, and WO 02/27049, published Apr. 4, 2002, thedisclosures of which are incorporated herein by reference. Othertechniques and other preferred conditions may be apparent those skilledin the art after reviewing the disclosure herein.

[0122] First, second, and third articles according to the presentinvention can be used to make fourth and fifth metal matrix compositescomposite articles according to the present invention. An example of afifth metal matrix composite article according to the present inventionis brake caliper for a vehicle (e.g., a motor vehicle such as a car,sports utility vehicle, van, or truck). Referring to FIG. 6, exemplarybrake caliper 60 comprises insert holder 61 and inserts 62A and 62B.

[0123] Typically, fourth and fifth metal matrix composite articlesaccording to the present invention comprise, in the region comprisingthe substantially continuous ceramic fibers, in the range from about 30to about 45 percent (in some embodiments, preferably about 35 to about45 percent, more preferably, about 35 to about 40 percent) by volumemetal and in the range from about 70 to about 55 percent (in someembodiments, preferably about 65 to about 55 percent, more preferably,about 60 to about 65 percent) by volume continuous ceramic oxide fibers,based on the total volume of the region. Further, the region comprisingthe ceramic oxide material and/or metal, as applicable, which securesthe substantially continuous ceramic oxide fibers, typically comprisesin the range from about 20 to about 95 percent (in some embodiments,preferably about 60 to about 90 percent, more preferably, about 80 toabout 85 percent) by volume metal and in the range from about 80 toabout 5 percent (in some embodiments, preferably about 60 to about 10percent, more preferably, about 15 to about 5 percent) by volume of theceramic oxide material and/or metal, based on the total volume of theregion.

[0124] In some embodiments, inserts comprise the substantiallycontinuous ceramic oxide fibers, in the range from about 30 to about 70percent (in some embodiments, preferably about 35 to about 60 percent,or even about 35 to about 45 percent) by volume metal and in the rangefrom about 70 to about 30 percent (in some embodiments, preferably about65 to about 40 percent, or even about 65 to about 55 percent) by volumesubstantially continuous ceramic oxide fibers, based on the total volumeof the insert. In some embodiments, preferably the inserts comprise atleast 50 by volume of the substantially continuous ceramic oxide fibers,based on the total volume of the insert.

[0125] The fiber and metal volume content of the fourth and fifth metalmatrix composite articles in the substantially continuous fiber regionis generally governed by the desired to produce a homogeneous compositewithout significant movement of the substantially continuous ceramicoxide fibers during the metal infiltration. If the fiber content is toolow, it is more difficult to prevent or minimize movement of thesubstantially continuous fibers during the metal infiltration. Forinserts comprising discontinuous fibers, in the discontinuous fiberregion, the fiber and metal volume content of the composite is, ingeneral, governed by balance between increased strength and stiffnessversus decreased ductility and machinability.

[0126] The particular fibers, matrix material(s), holder, etc. andprocess steps for making metal matrix composite articles are selected toprovide metal matrix composite articles with the desired properties. Forexample, the fibers and metal matrix materials are selected to besufficiently compatible with each other and the article fabricationprocess in order to make the desired article. The metal comprising themetal matrix composite in some embodiments is preferably selected suchthat the matrix material does not significantly react chemically withthe ceramic oxide material, (i.e., is relatively chemically inert withrespect to the metallic, refractory material), particularly thesubstantially continuous ceramic oxide fibers, for example, to eliminatethe need to provide a protective coating on the fiber exterior.

[0127] Additional details regarding some techniques for making aluminumand aluminum alloy matrix composites are disclosed, for example, inco-pending applications having U.S. Ser. Nos. 08/492,960, filed Jun. 21,1995 and 09/616,589, 09/616,593, and 09/616,594, filed Jul. 14, 2000,60/404,672, filed Aug. 20, 2002, and PCT application having publicationNo. WO 97/00976, published Jan. 9, 1997, the disclosures of which areincorporated herein by reference.

[0128] The metal comprising a metal comprising insert, holder, and/ormetal of a fourth or fifth metal matrix composite articles according tothe present invention may be the same or different. In some embodiments,the holder preferably comprises a 6000 series aluminum alloy and themetal of the fourth or fifth metal matrix composite articles accordingto the present invention comprises a 6000 series aluminum alloy. If theinsert is a metal comprising insert, in some embodiments, the metalcomprising the insert is preferably a 200 series metal.

[0129] Fourth and fifth metal matrix composite articles according to thepresent invention can be made using first, second, and third articlesaccording to the present invention using techniques known in the art(e.g., squeeze casting and permanent tool gravity casting). For porousinserts, such fabrication includes infiltrating the porous insert withmolten metal. Finite Element Analysis (FEA) modeling can be used, forexample, to identify optimal positions and quantities of the ceramicoxide fiber for meeting desired performance specifications. Suchanalysis can also be used, for example, to aid in selecting theconfiguration, composition, number, and location, for example of thefirst, second, and third article(s) according to the present inventionused. Typically, the insert(s) and/or die is preheated prior to casting.Although not wanting to be bound by theory, it is believed thatpreheating the first, second, and third fourth article(s) according tothe present invention facilitates desirable metallurgical bondingbetween the holder and/or insert(s) and the aluminum or aluminum alloyof the fourth or fifth metal matrix composite articles. In someembodiments of metal comprising inserts, preferably the insert(s) ispreheated to about 500° C.-600° C. In some embodiments of ceramiccomprising inserts, preferably the insert(s) is preheated to about 750°C.-800° C. In some embodiments, preferably the die is preheated to 200°C.-500° C. Although casting can typically be conducted in air, it isalso within the scope of the present invention to cast in otheratmospheres (e.g., argon).

[0130] FEA, may also be used, for example, to aid in choosing a castingtechnique, casting conditions, and/or mold design for casting an insertand/or metal matrix composite article according to the presentinvention. Suitable FEA software is commercially available, includingthat marketed by UES, Annapolis, Md., under the trade designation“PROCAST”. As discussed above, the articles according to the presentinvention are typically designed for a certain purpose, and as a result,it is desired to have certain properties, to have a certainconfiguration, be made of certain materials, etc. Typically, the mold isselected or made to provide the desired shape of the fourth or fifthmetal matrix composite articles to be cast so as to provide a net shapeor near net shape. Net-shaped or near net-shaped articles, can, forexample, minimize or eliminate the need for and cost of subsequentmachining or other post-casting processing of a cast metal matrixcomposite articles. Typically, the mold is made or adapted to hold theinsert(s) in a desired location(s) such that the substantiallycontinuous ceramic oxide fibers are properly positioned in the resultingmetal matrix composite articles. Techniques and materials for makingsuitable cavities are known to those skilled in the art. The material(s)from which a particular mold may be made depends, for example, on themetal used to make the metal matrix composite articles. Commonly usedmold materials include graphite or steel.

[0131] Again, surprisingly, first, second, and third articles accordingto the present invention can be used to make metal matrix compositearticles wherein the molten metal in the mold is in the molten state forless than 75 seconds (in some embodiments, preferably, less than 60seconds). Although longer times for keeping the molten metal in the moldin the molten state may also be useful, the shorter times (i.e., lessthan 75 seconds), and although not wanting to be bound by theory, it isbelieved that the longer times may lead to deformation of the holderand/or metal comprising insert(s). In some embodiments, preferably theholder and insert do not significantly deform during the casting of ametal matrix composite article (i.e., the holder and insert(s) havefirst outer dimensional configuration (i.e., size and shape) prior tocasting, and second outer dimensional shapes after casting, wherein therespective first and second outer dimensional configurations are thesame, and wherein it is understood that the metal having a positiveGibbs oxidation free energy above at least 200° C. and optional metalsuch as Ni tend to diffuse into the metal of the casting metal (andpossibly the metal of the insert)).

[0132] For metal matrix composite article having a higher than desiredamount of oxidation at the interface between the insert(s) and the metalcast around the insert, the article may be further processed using hotisostatic pressing (HIPing) to reduce or remove the undesired oxidation.HIPing may also be used to reduce the porosity, if any, in the metalmatrix composite article. Techniques for HIPing are well known in theart. Examples of HIPing temperatures, pressures, and times that may beuseful for embodiments of the present invention include 500° C. to 600°C., 25MPa to 50 MPa, and 4 to 6 hours, respectively. Temperatures,pressures, and times outside of these ranges may also be useful. Lowertemperatures tend, for example, to provide less densification and/orincrease the HIPing time, whereas higher temperatures may deform themetal matrix composite article. Lower pressures tend, for example, toprovide less densification and/or increase the HIPing time, whereashigher pressures tend, for example, to be unnecessary or in some cases,may even damage the metal matrix article. Shorter times tend, forexample, to provide less densification, whereas longer times may, forexample, be unnecessary.

[0133] For additional details on exemplary inserts and techniques formaking metal matrix composite articles see copending application havingU.S. Ser. No. 60/404,704, filed Aug. 20, 2002, the disclosure of whichis incorporated herein by reference.

[0134] Other techniques for making metal matrix composite articles maybe apparent to those skilled in the art after reviewing the instantdisclosure.

[0135] Additional details regarding making metal matrix composites canbe found, for example, in U.S. Pat. Nos. 4,705,093 (Ogino) and 5,234,080(Pantale), and 5,394,093 (Kennerknecht), the disclosures of which areincorporated herein by reference.

[0136] Further, for additional details regarding the formation ofceramic comprising inserts, and metal matrix composite article made fromceramic oxide pre-forms see, for example, U.S. applications having Ser.Nos. 09/966,946; 09/967,401; and 09/9677,562; filed Sep. 27, 2001 (andclaiming priority to provisional applications nos. 60/236,091;60/236,092; and 60/236,110; respectively, all filed Sep. 28, 2000), andPCT applications having publication nos. WO 02/26658, WO 02/27048, andWO 02/27049, published Apr. 4, 2002), the disclosures of which areincorporated herein by reference.

[0137] Embodiments of some metal matrix composite articles according tothe present invention have a “Peak Bond Strength Value” between theinsert or holder, as applicable (i.e., depending on which one is beingtested), and the aluminum or aluminum alloy cast around the insert asdetermined by the following “Peak Bond Strength Value Test” of at least100 MPa (in some embodiments, preferably at least 125 MPa, at least 150MPa, at least 175, or even at least 180 MPa). A schematic of thecompressive shear test equipment is shown in FIG. 9, wherein compressiveshear test equipment 140 includes pushout tool 141, test sample 142,support block 143, and 100,000 Newton (22,482 pounds) compressive loadcell 147. The metal matrix composite to be tested is cross-sectionedperpendicular to the longitudinal axis of the insert or holder, asapplicable; the thickness of the cross-section for the insert is 1.16 cm(0.46 inch), the thickness of the cross-section for the holder is 0.4cm, and the diameter of either 2.5 cm (1 inch).

[0138] Pushout tool 141 has a corresponding cross-section at the pointof contact with insert or holder, as applicable, 144 with test sample142, except the cross-sectional area of pushout tool 141 is 10 percentless (i.e., the shape of the cross-section of pushout tool 141 andinsert or holder, as applicable, 144 is the same, but the size of thecross-section of pushout tool 144 is less). Pushout tool 141 is clampedin upper jaws 145 of the hydraulic chuck with a hydraulic pressure of10.34 MPa (1500 pounds per square inch). Support block 143 has a 2.54 cm(1.0 inch) diameter by 0.15 cm (0.06 inch) deep counterbore. A 1.1 cm(0.435 inch) diameter through hole is placed on top of the open jaws 145of the bottom of hydraulic chuck 146.

[0139] Sample to be tested 142 is placed on top of support block 143 andnested in the counterbore for centering of the insert or holder, asapplicable, over the through hole. Bottom 148 of hydraulic chuck support146 is raised until the gap between the upper pushout tool 141, and theinsert or holder, as applicable, to be pushed out (i.e., sample to betested 144), is 0.025 cm. (0.01 inch). The exposed insert or holder, asapplicable, in the test specimen is then visually positioned with thematching tip of pushout tool 141 by manually sliding support block 143horizontally and rotationally until the cross-sections of the twoelements match.

[0140] The test is then conducted by moving the lower hydraulic supportchuck up toward fixed pushout tool 141 at a rate of 0.05 cm (0.020 inch)per minute while simultaneously monitoring the load and deflection. Theinsert or holder, as applicable, is thereby brought into contact withthe fixed pushout tool face and the contact force between the tworecorded as a function of displacement. The test is discontinued shortlyafter the peak force is reached and a total deflection of about 0.05 cm(0.020 inch) is obtained.

[0141] After completion of the test, the specimen is examined under anoptical microscope at 100× magnification to verify that the test insertor holder, as applicable, and pushout tip were properly aligned suchthat their cross-sections were overlapping.

[0142] The average shear stress is calculated using the followingformula:${{Average}\quad {Shear}\quad {Stress}} = \frac{\left. {{{Load}\quad {at}\quad {first}\quad {slippage}},{N\quad {{lbs}.}}} \right)}{{{Area}\quad {of}\quad {contact}\quad {between}\quad {insert}\quad {and}\quad {aluminum}\quad {alloy}},{m^{2}\quad {\left( {in}^{2} \right).}}}$

[0143] The loads are plotted as a function of the insert displacement.The load at which the pushout curve has a discontinuity (i.e., wherethere is initial slippage at the interface between the insert or holderand the aluminum or aluminum alloy cast around the insert or holder, asapplicable) is a peak bond strength value.

[0144] The Peak Bond Strength is calculated using Finite ElementAnalysis (FEA). Finite Element Analysis (FEA) software (available underthe trade designation “ANSYS” from Ansys Inc., Canonsburg, Pa.) is usedto model the insert or holder, as applicable, and show that the ratio ofpeak bond strength to measured average shear stress is approximately3.0.

[0145] The FEA calculation is done as follows. A finite element model ofthe test specimen geometry is created. The insert or holder, asapplicable, is meshed with elements of dimension 0.02 cm by 0.02 cm by0.05 cm (0.01 inch by 0.01 inch by 0.02 inch) cubes, except at the topof the insert or holder, as applicable, where the mesh size is 0.02 cmin all dimensions. The aluminum/aluminum alloy cast around the insert orholder, as applicable, is meshed with cubes having sides of 0.05 cm(0.02 inch) near the insert or holder, as applicable, and 0.10 cm (0.04inch) elsewhere in the modeled test specimen. The FEA software computesthe shear stress at points along the surface of the insert or holder, asapplicable, for an applied pressure of 533.3 MPa (corresponding to apushout test load of 2900 pounds). The calculation determines that thepeak shear stress across all points of the surface of the insert orholder, as applicable, and the average across the insert surface orholder surface, as applicable. The ratio of Peak Bond Strength toaverage shear stress is thus about 3 to 1.

[0146] Embodiments of some metal matrix composite articles according tothe present invention are free of oxygen at the interface between theinsert or holder and the aluminum or aluminum alloy cast around theinsert or holder as determined by the following “Oxygen Layer Test”. Aportion of a metal matrix composite article is cut to obtain across-section of the insert or holder and the aluminum or aluminum alloycast around the insert or holder. Then cross-section is polished withsemi-automatic metallographic grinding/polishing equipment (obtainedunder the trade name “ABRAMIN” from Struers, Inc, Cleveland, Ohio). Thepolishing speed is 150 rpm. The polishing is done in the followingsuccessive 6 stages. The polishing force is 150 N, except in Stage 6 itis 250 N:

[0147] Stage 1

[0148] The sample is polished for 45 seconds using 120 grit siliconcarbide paper (obtained from Pace Technologies, Northbrook, Ill.) whilecontinuously, automatically dripping water onto abrasive pad duringpolishing. After polishing, the sample is thoroughly rinsed with water.

[0149] Stage 2

[0150] The sample is polished for 45 seconds using 220 grit siliconcarbide paper (obtained from Pace Technologies) while continuously,automatically dripping water onto abrasive pad during polishing. Afterpolishing, the sample is thoroughly rinsed with water.

[0151] Stage 3

[0152] The sample is polished for 45 seconds using 600 grit siliconcarbide paper (obtained from Pace Technologies) while continuously,automatically dripping water onto abrasive pad during polishing. Afterpolishing, the sample is thoroughly rinsed with water.

[0153] Stage 4

[0154] The sample is polished for 4.5 minutes using polishing pad(obtained under the trade designation “DP-MOL” from Struers, Inc.),wetted lightly with periodic droplets of lubricant (obtained under thetrade designation “PURON, DP-LUBRICANT” from Struers) and sprayed for 1second with 6 micrometer diamond grit (obtained under the tradedesignation “DP-SPRAY, P-6 μm” from Struers). After polishing, thesample is thoroughly rinsed with water.

[0155] Stage 5

[0156] The sample is polished for 4.5 minutes using polishing pad(“DP-MOL”), wetted lightly with periodic droplets of lubricant (obtainedunder the trade designation “PURON, DP-LUBRICANT” from Struers) andsprayed for 1 second with 3 micrometer diamond grit (obtained under thetrade designation “DP-SPRAY, P-3 μm” from Struers). After polishing, thesample is thoroughly rinsed with water.

[0157] Stage 6

[0158] The sample is polished for 4.5 minutes using a porous syntheticpolishing cloth (obtained under the trade designation “OP-CHEM” fromStruers), wetted first with water and colloidal silica suspension(obtained under the trade designation “OP-S SUSPENSION” from Struers)poured by hand on the cloth. The sample is washed with water during thelast 5 seconds of polishing. After polishing, the sample is dried.

[0159] The resulting polished sample is viewed at 250× with opticalmicroscope to determine if a visibly discernable continuous oxide layeris present between the insert or holder and the aluminum or aluminumalloy cast around the insert or holder. For reference purposes, Example3 (see FIG. 10) of copending application having U.S. Ser. No.60/404,672, filed Aug. 20, 2002, the disclosure of which is incorporatedherein by reference, when evaluated with this test did not have avisibly discernable continuous oxide layer at the interface, whereasComparative Example H (see FIG. 11) from the same application did.Referring to FIG. 10, the polished cross-section of Example 3 showed noabrupt boundary at interface 162 between insert matrix 166 and castingalloy 163. Referring to FIG. 11, the polished cross-section ofComparative Example H showed an abrupt boundary, believed to be an oxidelayer, at interface 182 between insert matrix 186 and casting alloy 183.

[0160] An example of a disk brake for a motor vehicle comprises a rotor;inner and outer brake pads disposed on opposite sides of the rotor andmovable into braking engagement therewith; a piston for urging the innerbrake pad against the rotor; and a brake caliper comprising a bodymember having a cylinder positioned on one side of the rotor andcontaining the piston, an arm member positioned on the other side of therotor and supporting the outer brake pad, and a bridge extending betweenthe body member and the arm member across the plane of the rotor.

[0161] Referring to FIGS. 7A and 7B, disc brake assembly 70 comprisesbrake caliper housing 71 formed of body member 72, arm member 73, andbridge 74 connected at one end to body member 72 and at other end to armmember 73. Body member 72 has a generally cylindrical recess 75 thereinwhich slideably receives piston 76 to which is pressed inner brake pad77. Inner face 78 of arm member 73 supports outer brake pad 79 whichfaces inner brake pad 77. Brake rotor 701, connected to a wheel (notshown) of a vehicle, lies between inner and outer brake pads 77, 79,respectively. Brake caliper housing 71 includes inserts 200A and 200Bwith interfaces 202A and 202B. Hydraulic, or other, actuation of piston76 causes inner brake pad 77 to be urged against one side of rotor 701and, by reactive force, causes caliper housing 71 to float, therebybringing outer brake pad 79 into engagement with the other side of rotor701, as is well known in the art.

[0162] This invention is further illustrated by the following example,but the particular materials and amounts thereof recited in thisexample, as well as other conditions and details, should not beconstrued to unduly limit this invention. Various modifications andalterations of the invention will become apparent to those skilled inthe art. All parts and percentages are by weight unless otherwiseindicated.

EXAMPLE 1

[0163] An insert holder was made as follows. Aluminum sheet stock, 1.5mm in thickness, consisting of 6061 aluminum alloy that had beenheated-treated with a standard T4 heat treatment (obtained under thetrade designation “6061-T4” from Vincent Brass and Aluminum, St. Paul,Minn.) was laser-cut to obtain the configuration shown in FIG. 8. Thelaser used for cutting the aluminum sheet stock was a 1500 Watt,numerically controlled CO₂ laser (obtained from Coherent, Inc., SantaClara, Calif., and integrated into a numerically controlled lasercutting system by Laser Manufacturing, Inc., Somerset, Wis.). The insertholder was designed to hold three inserts, two with dimensions 72 mm by15.5 mm by 5 mm and one with dimensions 82 mm by 35 mm by 5 mm.

[0164] The cut sheet was bent with pliers along the fold lines a, b, c,d, e, f, g, and h shown in FIG. 8A to make the shape shown in FIGS. 8Aand 8B to provide an insert holder. Dimension A is 158.2 mm, B is 35 mm,C is 126.2 mm, D is 13.6 mm, and E is 28 mm. The insert holder was thencoated by Co-Operative Plating Co., St. Paul, Minn. to provide anelectroless deposition of about 3 micrometers of nickel followed by anelectroplating of about 12 micrometers of silver.

[0165] Inserts 13A, 13B, and 13C were placed in the holder and fastenedinto place by bending clamps 12A, 12B, 12C, and 12D shown in FIG. 1until they were just in contact with the inserts. Inserts 13A, 13B, and13C were made as follows.

[0166] Tows of continuous alpha alumina fibers (available under thetrade designation “NEXTEL 610” from the 3M Company, St. Paul, Minn.;3,000 denier; Young's modulus of about 370 GPa; average tensile strengthof about 3 GPa; average diameter 11 micrometers) were wound using adeionized water sizing, wherein the tows of fiber were dipped in a waterbath immediately before being wound onto a four-faced 20.3 cm. (8-inch)square mandrel to produce a fiber preform having a 65% volume loading offiber. The fiber was wound under tension (about 75 grams, as measured bya tension meter (obtained under the trade designation “CERTEN” fromTensitron, Boulder Colo.)) to form four rectangular preform plates (10.2cm (4 inches) by 20.3 cm (8 inches) by 0.29 cm (0.115 inches) thick).The mandrel was then placed in a −40° C. (−40° F.) cooler to freeze thewater and stabilize the resulting preform. When frozen, the plates werecut into 7.6 cm by 15.2 cm (3 inch by 6 inch) preforms.

[0167] A graphite die assembly (obtained from Schunk GraphiteTechnology, Inc., Menomonie Falls, Wis.) was used to cast the aluminummatrix composite plates. The width of the graphite die was 9.64 cm, thelength 15.24 cm and the height 4.90 cm. The die included four slots forinserts with 0.89 cm center-to-center spacing between the slots. Thegraphite die assembly was coated with an aqueous graphite particledispersion (obtained under the trade designation “AQUADAG” from AchesonColloids Company, Port Huron, Mich.). Four of the frozen 7.6 cm by 15.2cm preforms were placed in the graphite die assembly, one preform ineach of the four cavities. The die assembly with the preforms positionedtherein was then placed in an oven at 120° C. (250° F.) for about 16hours until the water in the preforms evaporated.

[0168] The die assembly was then placed in a stainless steel can (length102 mm, width 53 mm, and height 500 mm) open at one end, and having itsinterior coated with a boron nitride suspension (obtained under thetrade designation “RS 1000” from ZYP Coatings Inc., Oak Ridge, Tenn.).Although not wanting to be bound by theory, it is believed that theboron nitride coating inhibits reaction between the stainless steel andthe molten aluminum during the subsequent casting operation.

[0169] After the coating was dry, 2500 grams of an aluminum-2% copperalloy ingot (cut into two pieces, each 5.1 cm by 2.5 cm by 30.5 cm (Iinch by 2 inch by 12 inch)) (obtained under the trade designation“1980-A” from Belmont Metal, New York, N.Y.) were then placed in thestainless steel can on top of the assembly. A type-K thermocouple(obtained from Omega Engineering Inc., Stamford, Conn.) was placed atthe top of the die assembly to monitor the temperature of thealuminum-2% copper melt during the casting process. A hold-down rod wasalso affixed to the top of the graphite assembly to prevent thatassembly from floating in the molten aluminum during the casting. Thestainless steel can was then placed inside the pressure vessel of thepressure casting machine (obtained from Process EngineeringTechnologies, Plaistow, N.H.), and the pressure vessel closed. The sizeof the pressure casting vessel was about 16.9 cm (inner diameter) by88.9 cm (in length).

[0170] The closed casting vessel was then evacuated of air with a vacuumpump until a pressure of less than one torr was achieved. The power tothe electrical furnace of the pressure caster was then turned on, andthe graphite die assembly and Al-2%Cu alloy ingot were heated to atemperature of 710° C. (about 100° C. above the melting point of thealloy). The average heating rate was about 340° C. per hour. After amelt temperature of 710° C. was reached, the furnace power was turnedoff, and the vacuum valve to the vessel closed, thereby isolating thevessel from the vacuum pump.

[0171] A low pressure valve connected to pressurized, bottled argontanks was then opened to back-fill the vessel with argon to an initiallow pressure of 1.79 MPa (260 psi). When this pressure was reached, thelow-pressure valve was closed and a high-pressure argon valve was openeduntil a pressure of 8.96 MPa (1300 psi) was reached. The pressure wasmaintained at 8.96 MPa±1% (1300 psi±15 psi) for 15-20 minutes forcingthe molten aluminum-2% copper alloy to infiltrate the preformscompletely.

[0172] Next, the pressure was allowed to decay with the temperature to500° C. When the temperature fell below 500° C., the vessel exhaustvalve was opened, and the argon was vented to the atmosphere. The vesselwas then opened, and the stainless steel can was removed. The dieassembly was separated from the can, and the four cast aluminum matrixcomposite plates were removed from the graphite mold.

[0173] The cast plates were surface ground with a vertical spindlediamond grinder (#11 Blanchard grinder obtained from PrecisionInstruments, Minneapolis, Minn.) to a thickness of 0.25 cm (0.1 inch).The plates were then sliced lengthwise to a width of 0.94 cm (0.37 inch)to make 15.2 cm (6 inch) by 0.95 cm (0.375 inch) by 0.25 cm (0.1 inch)plates.

[0174] Three plates were then surface treated/coated as follows. Allplates were abraded with a 100 grit grinder wheel (obtained under thetrade designation “DIAMOND WHEEL, ASD100” from Norton Company,Worcester, Mass.), and cleaned with a standard lacquer thinner(available as Grade 401 from HCI, St. Paul, Minn.) by rubbing with papertowels until no visible residue could be removed from the surface.

[0175] The two resulting plates were coated (by Co-Operative PlatingCo., St. Paul, Minn.), via electroless deposition, with about 3micrometers of nickel, followed by electroplating about 12 micrometersof silver. The holder and inserts were provided by the 3M Company to THTPresses, Inc., Dayton Ohio for them to use to squeeze cast, using 354aluminum alloy, the resulting brake caliper shown in FIG. 6.

EXAMPLE 2

[0176] A portion of an exemplary holder according to the presentinvention was prepared as follows. A piece of sheet stock of 6061aluminum (obtained under the trade designation “6061-T4” from VincentBrass and Aluminum, St. Paul Minn.) was cut by Eagle Tool (Spring LakePark, Minn.) using a water-jet cutting process. The resulting sheet was0.095 inch (0.24 cm) in thickness. The cutout piece had dimensions 0.367inch by 0.095 inch by 6.00 inch (0.93 cm by 0.24 cm by 15.24 cm). Theedges of the aluminum piece were smoothed using 150 grit sandpaper toremove the slight ripples from water-jet cutting. To facilitate laterinsertion of the portion into a die, one end of the aluminum piece wastapered using 150 grit sandpaper (available from 3M Company, St. Paul,Minn. under the trade designation “WETORDRY”) to a 0.327 inch by 0.055inch (0.83 cm by 0.14 cm) section over the final 0.40 inch (1.0 cm) ofits length.

[0177] The resulting aluminum piece was then plated (by Co-OperativePlating Co, St. Paul, Minn.) with an electroless coating of nickelfollowed by electroplating with silver). The thickness of the nickelcoating was about 3 micrometers, and the silver coating about 17micrometers.

[0178] The resulting exemplary holder portion was heated in air byplacing the holder portion for 20 minutes in a furnace preheated toabout 550° C. The heated holder portion was then placed in a steel diecavity. Referring to FIG. 12, die 130 included base 132 (9.8 cm by 9.8cm by 14 cm (3.9 in. by 3.9 in. by 5.5 in.)) with rectangular slot 134(1.3 cm by 0.25 cm (0.5 in. by 0.1 in.)) for the holder portion, andupper part 136 (7.3 cm by 7.3 cm by 12.7 cm (29 in by 2.9 in by 5.0in)). Upper part 136 includes cavity 138 having diameter 2.54 cm (1inch) and depth 10.2 cm (4 inch). Upper part 136 was coated with a boronnitride release agent (obtained under the trade designation “COMBATBORON NITRIDE AEROSOL SPRAY CC-18” from The Carborundum Corp., Amherst,N.Y.) and then preheated to about 400° C. Within four seconds after theheated holder portion was placed in the die, a molten aluminum alloy(obtained under the trade designation “A356” from Alcan Inc., Montreal,Quebec) at a temperature of about 760° C. was poured into the steel diecavity around the pre-heated holder portion and allowed to solidify.When the temperature cooled to about 500° C., the holder portion andcasting assembly were removed from the die cavity.

[0179] The resulting cast sample was heat-treated by placing it in anoven for 8 hours at 535° C., followed by a water quench, and concludingwith 12 hours in an oven at 160° C.

[0180] The resulting heat-treated sample was sectioned into four 0.27 cm(0.106 inch) by 2.5 cm (1 inch) diameter sections. These four sectionswere cut perpendicular to the longitudinal axis of the exemplary portionof the holder. For each of the four sections, an “L”-shaped piece ofaluminum (cut from the sheet stock aluminum (“6061-T4”) 0.040 inch (0.10cm) thick was adhered (marketed under the trade designation “PRONTO CA8”from 3M Company, St. Paul, Minn.) to each section to mark the boundarybetween the exemplary portion of the holder and the surrounding 356aluminum alloy to facilitate alignment during the pushout test.

[0181] A schematic of the compressive shear test equipment is shown inFIG. 9, wherein compressive shear test equipment 140 included pushouttool 141, test sample 142, support block 143, and 100,000 Newton (22,482pounds) compressive load cell 147. Pushout tool 141 had a correspondingcross-section at the point of contact with the exemplary portion of theholder, 144 with test sample 142, except the cross-sectional area ofpushout tool 141 was 10 percent less (i.e., the shape of thecross-section of pushout tool 141 and exemplary portion of the holder,144 was the same, but the size of the cross-section of pushout tool 144is less). Pushout tool 141 was clamped in upper jaws 145 of thehydraulic chuck with a hydraulic pressure of 10.34 MPa (1500 pounds persquare inch). Support block 143 had a 2.54 cm (1.0 inch) diameter by0.15 cm (0.06 inch) deep counterbore. A 1.1 cm (0.435 inch) diameterthrough hole was placed on top of the open jaws 145 of the bottom ofhydraulic chuck 146.

[0182] Sample to be tested 142 was placed on top of support block 143and nested in the counterbore for centering of the exemplary portion ofthe holder over the through hole. Bottom 148 of hydraulic chuck support146 was raised until the gap between the upper pushout tool 141, and theexemplary portion of the holder to be pushed out (i.e., sample to betested 144), was 0.025 cm. (0.01 inch). The exposed exemplary portion ofthe holder in the test specimen was then positioned to line up with thealignment strip previously glued to the sample with the matching tip ofpushout tool 141 by manually sliding support block 143 horizontally androtationally until the cross-sections of the two elements match.

[0183] The test was then conducted by moving the lower hydraulic supportchuck up toward fixed pushout tool 141 at a rate of 0.025 cm (0.010inch) per minute while simultaneously monitoring the load anddeflection. The exemplary portion of the holder was thereby brought intocontact with the fixed pushout tool face and the contact force betweenthe two was recorded as a function of displacement. The test wasdiscontinued shortly after a total deflection of about 0.05 cm (0.020inch) was obtained.

[0184] After completion of the test, the specimen was examined under anoptical microscope at 100× magnification to verify that the exemplaryportion of the holder and pushout tip were properly aligned such thattheir cross-sections were overlapping.

[0185] The average shear stress is calculated using the followingformula:${{Average}\quad {Shear}\quad {Stress}} = \frac{\left. {{{Load}\quad {at}\quad {first}\quad {slippage}},{N\quad {{lbs}.}}} \right)}{\begin{matrix}{{Area}\quad {of}\quad {contact}\quad {between}\quad {holder}\quad {portion}} \\{{{and}\quad {aluminum}\quad {alloy}},{m^{2}\quad {\left( {in}^{2} \right).}}}\end{matrix}}$

[0186] The loads were plotted as a function of the displacement of theexemplary portion of the holder. The load at which the pushout curveshowed significant nonlinear deflection (i.e., where there was initialslippage at the interface between the exemplary portion of the holderand the aluminum or aluminum alloy cast around the exemplary portion ofthe holder) was a peak bond strength value.

[0187] The Peak Bond Strength was calculated using Finite ElementAnalysis (FEA). Finite Element Analysis (FEA) software (obtained underthe trade designation “ANSYS” from Ansys Inc., Canonsburg, Pa.) was usedto model the exemplary portion of the holder, and show that the ratio ofpeak bond strength to measured average shear stress was about 1.86.

[0188] The FEA calculation was done as follows. A finite element modelof the test specimen geometry was created. The exemplary portion of theholder was meshed with cube-shaped elements 0.025 cm (0.01 inch) insize. The aluminum/aluminum alloy cast around the exemplary portion ofthe holder was meshed with cubes having sides of 0.025 cm (0.01 inch)near the exemplary portion of the holder and 0.10 cm (0.04 inch)elsewhere in the modeled test specimen. The FEA software computed theshear stress at points along the surface of the exemplary portion of theholder for an applied pressure of 228 MPa (corresponding to a pushouttest load of 1144 pounds). The calculation then determined the peakshear stress across all points of the surface of the exemplary portionof the holder and the average across the exemplary portion of the holdersurface, as applicable. The ratio of Peak Bond Strength to average shearstress thus obtained was about 1.86 to 1 for an exemplary portion of aholder surface. The load at first slippage, the average shear stress,and the peak bond strength for the four samples (Examples 2A, 2B, 2C,and 2D) are reported in the Table below. TABLE Load at first AverageShear Peak Bond Strength, Example slippage, N, (lbs.) Stress, MPa, (psi)MPa, (psi) 2A 4466 (1004) 70.8 (10,266) 131.7 (19,095) 2B 5418 (1218)85.9 (12,454) 159.7 (23,165) 2C 5218 (1173) 83.7 (12,131) 155.6 (22,564)2D 4942 (1111) 79.7 (11,567) 148.3 (21,515)

[0189] Various modifications and alterations of this invention willbecome apparent to those skilled in the art without departing from thescope and spirit of this invention, and it should be understood thatthis invention is not to be unduly limited to the illustrativeembodiments set forth herein.

What is claimed is:
 1. An article comprising: an insert holder includingat least one portion for securing at least one insert, the insert holdercomprising a first metal selected from the group consisting of aluminum,alloys thereof, and combinations thereof, the insert holder having anouter surface, and a second metal on the outer surface of the firstmetal, the second metal having a positive Gibbs oxidation free energyabove at least 200° C., the second metal having a thickness of at least8 micrometers; and at least one metal comprising reinforcement insertsecured in at least one portion for securing at least one insert.
 2. Thearticle according to claim 1 comprising two portions for securingrespectively an insert, and two of the metal comprising reinforcementinserts positioned respectively in the portions for securingrespectively an insert.
 3. The article according to claim 1 furthercomprising a third metal between the second metal and the outer surfaceof the first metal.
 4. The article according to claim 1 wherein thesecond metal has a thickness of at least 10 micrometers.
 5. The articleaccording to claim 1 wherein the second metal is one of gold or silver.6. The article according to claim 1 wherein the first metal is analuminum alloy, and wherein the metal of the metal comprisingreinforcement insert is an aluminum alloy.
 7. The article according toclaim 1 wherein the first metal is a 6000 series aluminum alloy andwherein the metal of the metal comprising reinforcement insert is a 200series aluminum alloy.
 8. An article comprising: an insert holderincluding at least one portion for securing at least one insert, theinsert holder comprising a first metal selected from the groupconsisting of aluminum, alloys thereof, and combinations thereof, theinsert holder having an outer surface, and a second metal on the outersurface of the first metal, the second metal having a positive Gibbsoxidation free energy above at least 200° C., the second metal having athickness of at least 8 micrometers; and at least one crystallineceramic comprising reinforcement insert secured in at least one portionfor securing at least one insert.
 9. The article according to claim 8wherein the second metal has a thickness of at least 10 micrometers. 10.The article according to claim 8 wherein the second metal is one of goldor silver.
 11. The article according to claim 9 wherein the crystallineceramic comprising reinforcement insert comprises porous, sinteredceramic oxide material and substantially continuous ceramic oxide fibershaving lengths of at least 5 cm, the porous, sintered ceramic oxidematerial securing the substantially continuous ceramic oxide fibers inplace, wherein the porous, sintered ceramic oxide material extends alongat least a portion of the length of the substantially continuous fibers.12. An article comprising: an insert holder including at least oneportion for securing at least one insert, the insert holder comprises afirst metal selected from the group consisting of aluminum, alloysthereof, and combinations thereof, the insert holder having an outersurface, Ni on the outer surface of the insert holder, the Ni having anouter surface; and Ag on the outer surface of the Ni, the Ag having athickness of at least 8 micrometers; and at least one metal comprisingreinforcement insert secured in the at least one portion for securing atleast one insert.
 13. The article according to claim 12 wherein the Nihas a thickness of at least 1 micrometer.
 14. An article comprising: aninsert holder including at least one portion for securing at least oneinsert, the insert holder comprises a first metal selected from thegroup consisting of aluminum, alloys thereof, and combinations thereof,the insert holder having an outer surface, Ni on the outer surface ofthe insert holder, the Ni having an outer surface; and Ag on the outersurface of the Ni, the Ag having a thickness of at least 8 micrometers;and at least one crystalline ceramic comprising reinforcement insertsecured in the at least one portion for securing at least one insert.15. The article according to claim 14 wherein the Ni has a thickness ofat least 1 micrometer.
 16. The article according to claim 14 wherein thecrystalline ceramic comprising reinforcement insert comprises porous,sintered ceramic oxide material and substantially continuous ceramicoxide fibers having lengths of at least 5 cm, the porous, sinteredceramic oxide material securing the substantially continuous ceramicoxide fibers in place, wherein the porous, sintered ceramic oxidematerial extends along at least a portion of the length of thesubstantially continuous fibers.
 17. An article comprising: an insertholder including at least one portion for securing at least one insert,the insert holder comprises a first metal selected from the groupconsisting of aluminum, alloys thereof, and combinations thereof, theinsert holder having an outer surface, and a second metal on the outersurface of the first metal, the second metal having a positive Gibbsoxidation free energy above at least 200° C.; and at least one metalmatrix composite insert secured in at least one portion for securing atleast one insert, wherein at least one of such inserts comprises:substantially continuous ceramic oxide fibers and third metal selectedfrom the group consisting of aluminum, alloys thereof, and combinationsthereof, wherein the third metal secures the substantially continuousceramic oxide fibers in place, and wherein the third metal extends alongat least a portion of the length of the substantially continuous ceramicoxide fibers, the third metal having an outer surface; and a fourthmetal on the outer surface of the third metal, the fourth metal having apositive Gibbs oxidation free energy above at least 200° C., and thefourth metal having a thickness of at least 8 micrometers.
 18. Thearticle according to claim 17 further comprising another metal betweenthe second metal and the outer surface of the first metal, and, furthercomprising another metal between the fourth metal and the outer surfaceof the third metal.
 19. The article according to claim 17 wherein thesecond and fourth metals each have a thickness of at least 10micrometers.
 20. The article according to claim 17 wherein the secondand fourth metals are one of gold or silver.
 21. The article accordingto claim 17 wherein the first metal is an aluminum alloy, and whereinthe third metal is an aluminum alloy.
 22. The article according to claim17 wherein the first metal is a 6000 series aluminum alloy and whereinthe third metal is a 200 series aluminum alloy.
 23. An articlecomprising: an insert holder including at least one portion for securingat least one insert, the insert holder comprises a first metal selectedfrom the group consisting of aluminum, alloys thereof, and combinationsthereof; and at least one metal matrix composite insert positioned inthe at least one portion for securing at least one insert, the insertcomprising substantially continuous ceramic oxide fibers and secondmetal selected from the group consisting of aluminum, alloys thereof,and combinations thereof, wherein the second metal secures thesubstantially continuous ceramic oxide fibers in place, and wherein thesecond metal extends along at least a portion of the length of thesubstantially continuous ceramic oxide fibers, the insert holder withthe at least one insert secured in the at least one portion for securingat least one insert collectively having an outer surface, and a thirdmetal on the outer surface, the third metal having a positive Gibbsoxidation free energy above at least 200° C., and the third metal havinga thickness of at least 8 micrometers.
 24. The article according toclaim 23 further comprising another metal between the third metal andthe outer surface.
 25. The article according to claim 24 wherein thethird metal has a thickness of at least 10 micrometers.
 26. The articleaccording to claim 24 wherein the third metal is one of gold or silver.27. The article according to claim 24 wherein the first metal is analuminum alloy, and wherein the second metal is an aluminum alloy. 28.The article according to claim 24 wherein the first metal is a 6000series aluminum alloy and wherein the second metal is a 200 seriesaluminum alloy.
 29. An article comprising: an insert holder including atleast one portion for securing at least one insert, the insert holdercomprises a first metal selected from the group consisting of aluminum,alloys thereof, and combinations thereof, the insert holder having anouter surface, Ni on the outer surface of the insert holder, the Nihaving an outer surface; and Ag on the outer surface of the Ni; and atleast one a metal matrix composite insert secured in the at least oneportion for securing at least one insert, at least one of such insertscomprising: substantially continuous ceramic oxide fibers and secondmetal selected from the group consisting of aluminum, alloys thereof,and combinations thereof, wherein the second metal secures thesubstantially continuous ceramic oxide fibers in place, and wherein thesecond metal extends along at least a portion of the length of thesubstantially continuous ceramic oxide fibers, the second metal havingan outer surface; Ni on the outer surface of the second metal, the Nihaving an outer surface; and Ag on the outer surface of the Ni, the Aghaving a thickness of at least 8 micrometers.
 30. The article accordingto claim 29 wherein the Ni has a thickness of at least 1 micrometer. 31.An article comprising: an insert holder including at least one portionfor securing at least one insert, the insert holder comprises a firstmetal selected from the group consisting of aluminum, alloys thereof,and combinations thereof; and at least one metal matrix composite insertpositioned in the at least one portion for securing at least one insert,the insert comprising substantially continuous ceramic oxide fibers andsecond metal selected from the group consisting of aluminum, alloysthereof, and combinations thereof, wherein the second metal secures thesubstantially continuous ceramic oxide fibers in place, and wherein thesecond metal extends along at least a portion of the length of thesubstantially continuous ceramic oxide fibers, the insert holder withthe at least one insert secured in the at least one portion for securingat least one insert collectively having an outer surface, Ni on theouter surface of the metal, the Ni having an outer surface of the insertholder, and Ag on the outer surface of the Ni.
 32. The article accordingto claim 31 wherein the Ni has a thickness of at least 1 micrometer. 33.A metal matrix composite article comprising a first metal and an insertholder including at least one portion for securing at least one insert,wherein the first metal selected from the group consisting of aluminum,alloys thereof, and combinations thereof, wherein the insert holdercomprises: a second metal selected from the group consisting ofaluminum, alloys thereof, and combinations thereof; and at least onemetal comprising reinforcement insert secured in the at least oneportion for securing at least one insert, wherein there is an interfacelayer between the first metal and the insert holder, and wherein thereis an interface layer peak bond strength value between the first metaland the insert holder of at least 100 MPa.
 34. The metal matrixcomposite article according to claim 33 wherein the peak bond strengthvalue is at least 130 MPa.
 35. The metal matrix composite articleaccording to claim 33 comprising two portions for securing respectivelyan insert, and two of the metal comprising reinforcement insertspositioned respectively in the portions for securing respectively aninsert.
 36. The metal matrix composite article according to claim 33wherein the first metal is an aluminum alloy, wherein the second metalis an aluminum alloy, and wherein the metal of the metal comprisingreinforcement insert is an aluminum alloy.
 37. The metal matrixcomposite article according to claim 33 wherein the first metal is oneof a 300 or 400 series aluminum alloy, wherein the second metal is a6000 series aluminum alloy, and wherein the metal of the metalcomprising reinforcement insert is 200 series aluminum alloy.
 38. Themetal matrix composite article according to claim 33 which is a brakecaliper.
 39. A disc brake for a motor vehicle comprising a rotor; innerand outer brake pads disposed on opposite sides of the rotor and movableinto braking engagement therewith; a piston for urging the inner brakepad against the rotor; and the brake caliper according to claim 38comprising a body member having a cylinder positioned on one side of therotor and containing the piston, an arm member positioned on the otherside of the rotor and supporting the outer brake pad, and a bridgeextending between the body member and the arm member across the plane ofthe rotor.
 40. A metal matrix composite article comprising a first metaland an insert holder including at least one portion for securing atleast one insert, wherein the first metal selected from the groupconsisting of aluminum, alloys thereof, and combinations thereof,wherein the insert holder comprises: a second metal selected from thegroup consisting of aluminum, alloys thereof, and combinations thereof;and at least one crystalline ceramic comprising reinforcement insertsecured in the at least one portion for securing at least one insert,wherein there is an interface layer between the first metal and theinsert holder, and wherein there is an interface layer peak bondstrength value between the first metal and the insert holder of at least100 MPa.
 41. The metal matrix composite article according to claim 40wherein the peak bond strength value is at least 130 MPa.
 42. The metalmatrix composite article according to claim 40 comprising two portionsfor securing respectively an insert, and two of the crystalline ceramiccomprising reinforcement inserts positioned respectively in the portionsfor securing respectively an insert.
 43. The metal matrix compositearticle according to claim 40 wherein the first metal is an aluminumalloy and wherein the second metal is an aluminum alloy.
 44. The metalmatrix composite article according to claim 40 wherein the first metalis one of a 300 or 400 series aluminum alloy, and wherein the secondmetal is a 6000 series aluminum alloy.
 45. The metal matrix compositearticle according to claim 44 wherein the crystalline ceramic comprisingreinforcement insert comprises porous, sintered ceramic oxide materialand substantially continuous ceramic oxide fibers having lengths of atleast 5 cm, the porous, sintered ceramic oxide material securing thesubstantially continuous ceramic oxide fibers in place, wherein theporous, sintered ceramic oxide material extends along at least a portionof the length of the substantially continuous fibers.
 46. The metalmatrix composite article according to claim 40 which is a brake caliper.47. A disc brake for a motor vehicle comprising a rotor; inner and outerbrake pads disposed on opposite sides of the rotor and movable intobraking engagement therewith; a piston for urging the inner brake padagainst the rotor; and the brake caliper according to claim 46comprising a body member having a cylinder positioned on one side of therotor and containing the piston, an arm member positioned on the otherside of the rotor and supporting the outer brake pad, and a bridgeextending between the body member and the arm member across the plane ofthe rotor.
 48. A metal matrix composite article comprising a first metaland an insert holder including at least one portion for securing atleast one insert, wherein the first metal selected from the groupconsisting of aluminum, alloys thereof, and combinations thereof,wherein the insert holder comprises: a second metal selected from thegroup consisting of aluminum, alloys thereof, and combinations thereof;and at least one metal matrix composite insert secured in the at leastone portion for securing at least one insert, the metal matrix compositeinsert comprising: substantially continuous ceramic oxide fibers andthird metal selected from the group consisting of aluminum, alloysthereof, and combinations thereof, wherein the third metal secures thesubstantially continuous ceramic oxide fibers in place, and wherein thethird metal extends along at least a portion of the length of thesubstantially continuous ceramic oxide fibers, wherein there is aninterface layer between the first metal and the insert holder, whereinthe interface layer is free of oxygen, wherein the interface layerincludes an average amount of a fourth metal having a positive Gibbsoxidation free energy above at least 200° C., and wherein the averageamount of the fourth metal in the interface layer is higher in theinterface layer than that present in the first metal.
 49. The metalmatrix composite article according to claim 48 comprising two portionsfor securing respectively an insert, and two of the metal matrixcomposite inserts positioned respectively in the portions for securingrespectively an insert.
 50. The metal matrix composite article accordingto claim 48 wherein the first metal is an aluminum alloy, wherein thesecond metal is an aluminum alloy, and wherein the third metal is analuminum alloy.
 51. The metal matrix composite article according toclaim 48 wherein the first metal is one of a 300 or 400 series aluminumalloy, wherein the second metal is a 6000 series aluminum alloy, andwherein the third metal is a 200 series aluminum alloy.
 52. The metalmatrix composite article according to claim 48 which is a brake caliper.53. A disc brake for a motor vehicle comprising a rotor; inner and outerbrake pads disposed on opposite sides of the rotor and movable intobraking engagement therewith; a piston for urging the inner brake padagainst the rotor; and the brake caliper according to claim 52comprising a body member having a cylinder positioned on one side of therotor and containing the piston, an arm member positioned on the otherside of the rotor and supporting the outer brake pad, and a bridgeextending between the body member and the arm member across the plane ofthe rotor.
 54. A metal matrix composite article comprising a first metaland an insert holder including at least one portion for securing atleast one insert, wherein the first metal selected from the groupconsisting of aluminum, alloys thereof, and combinations thereof,wherein the insert holder comprises: a second metal selected from thegroup consisting of aluminum, alloys thereof, and combinations thereof;and at least one metal matrix composite insert secured in the at leastone portion for securing at least one insert, the metal matrix compositeinsert comprising: substantially continuous ceramic oxide fibers andthird metal selected from the group consisting of aluminum, alloysthereof, and combinations thereof, wherein the third metal secures thesubstantially continuous ceramic oxide fibers in place, and wherein thethird metal extends along at least a portion of the length of thesubstantially continuous ceramic oxide fibers, wherein there is aninterface layer between the first metal and the insert holder, andwherein there is an interface layer peak bond strength value between thefirst metal and the insert holder of at least 100 MPa.
 55. The metalmatrix composite article according to claim 54 wherein the peak bondstrength value is at least 130 MPa.
 56. The metal matrix compositearticle according to claim 54 comprising two portions for securingrespectively an insert, and two of the metal matrix composite insertspositioned respectively in the portions for securing respectively aninsert.
 57. The metal matrix composite article according to claim 54wherein the first metal is an aluminum alloy, wherein the second metalis an aluminum alloy, and wherein the third metal is an aluminum alloy.58. The metal matrix composite article according to claim 54 wherein thefirst metal is one of a 300 or 400 series aluminum alloy, wherein thesecond metal is a 6000 series aluminum alloy, and wherein the thirdmetal is a 200 series aluminum alloy.
 59. The metal matrix compositearticle according to claim 54 which is a brake caliper.
 60. A disc brakefor a motor vehicle comprising a rotor; inner and outer brake padsdisposed on opposite sides of the rotor and movable into brakingengagement therewith; a piston for urging the inner brake pad againstthe rotor; and the brake caliper according to claim 59 comprising a bodymember having a cylinder positioned on one side of the rotor andcontaining the piston, an arm member positioned on the other side of therotor and supporting the outer brake pad, and a bridge extending betweenthe body member and the arm member across the plane of the rotor.
 61. Ametal matrix composite article comprising a first metal and an insertholder including at least one portion for securing at least one insert,wherein the first metal selected from the group consisting of aluminum,alloys thereof, and combinations thereof, wherein the insert holdercomprises: a second metal selected from the group consisting ofaluminum, alloys thereof, and combinations thereof; and at least onemetal matrix composite insert secured in the at least one portion forsecuring at least one insert, the metal matrix composite insertcomprising: substantially continuous ceramic oxide fibers and thirdmetal selected from the group consisting of aluminum, alloys thereof,and combinations thereof, wherein the third metal secures thesubstantially continuous ceramic oxide fibers in place, and wherein thethird metal extends along at least a portion of the length of thesubstantially continuous ceramic oxide fibers, wherein there is aninterface layer between the first metal and the insert holder, whereinthe interface layer is free of oxygen, and wherein the interface layerincludes an average amount of Ag and Ni higher than that present in thefirst metal.
 62. The metal matrix composite article according to claim61 wherein the peak bond strength value is at least 130 MPa.
 63. Themetal matrix composite article according to claim 61 comprising twoportions for securing respectively an insert, and two of the metalmatrix composite inserts positioned respectively in the portions forsecuring respectively an insert.
 64. The metal matrix composite articleaccording to claim 61 wherein the first metal is an aluminum alloy,wherein the second metal is an aluminum alloy, and wherein the thirdmetal is an aluminum alloy.
 65. The metal matrix composite articleaccording to claim 61 wherein the first metal is one of a 300 or 400series aluminum alloy, wherein the second is a 6000 series aluminumalloy, and wherein the third metal is a 200 series aluminum alloy. 66.The metal matrix composite article according to claim 61 which is abrake caliper.
 67. A disc brake for a motor vehicle comprising a rotor;inner and outer brake pads disposed on opposite sides of the rotor andmovable into braking engagement therewith; a piston for urging the innerbrake pad against the rotor; and the brake caliper according to claim 66comprising a body member having a cylinder positioned on one side of therotor and containing the piston, an arm member positioned on the otherside of the rotor and supporting the outer brake pad, and a bridgeextending between the body member and the arm member across the plane ofthe rotor.
 68. A method of making a metal matrix composite article, themethod comprising: positioning an insert holder that includes a metalcomprising reinforcement insert, the insert holder including at leastone portion for securing at least one insert, the insert holdercomprising a first metal selected from the group consisting of aluminum,alloys thereof, and combinations thereof, the insert holder having anouter surface, and a second metal on the outer surface of the firstmetal, the second metal having a positive Gibbs oxidation free energyabove at least 200° C., the second metal having a thickness of at least8 micrometers, and the metal comprising reinforcement insert beingsecured in the at least one portion for securing at least one insert;providing molten third metal selected from the group consisting ofaluminum, alloys thereof, and combinations thereof into the mold; andcooling the molten third metal to provide a metal matrix compositearticle.
 69. The method according to claim 68 wherein the molten thirdmetal in the mold is in the molten state for less than 75 seconds. 70.The method according to claim 68 wherein the molten third metal in themold is in the molten state for less than 75 seconds.
 71. The methodaccording to claim 68 comprising two portions for securing respectivelyan insert, and two of the metal comprising reinforcement insertspositioned respectively in the portions for securing respectively aninsert.
 72. The method according to claim 68 wherein the first metal isan aluminum alloy, wherein the third metal is an aluminum alloy, andwherein the metal of the metal comprising reinforcement insert is analuminum alloy.
 73. The method according to claim 68 wherein the firstmetal is a 6000 series aluminum alloy, wherein the metal of the metalcomprising reinforcement insert is a 200 series aluminum alloy, andwherein the third metal is one of a 300 or 400 series aluminum alloy.74. The method according to claim 68 wherein the metal matrix compositearticle is a brake caliper.
 75. A method of making a metal matrixcomposite article, the method comprising: positioning an insert holderthat includes a crystalline ceramic comprising reinforcement insert, theinsert holder including at least one portion for securing at least oneinsert, the insert holder comprising a first metal selected from thegroup consisting of aluminum, alloys thereof, and combinations thereof,the insert holder having an outer surface, and a second metal on theouter surface of the first metal, the second metal having a positiveGibbs oxidation free energy above at least 200° C., the second metalhaving a thickness of at least 8 micrometers, and the crystallineceramic comprising reinforcement insert being secured in the at leastone portion for securing at least one insert; providing molten thirdmetal selected from the group consisting of aluminum, alloys thereof,and combinations thereof into the mold; and cooling the molten thirdmetal to provide a metal matrix composite article.
 76. The methodaccording to claim 75 wherein the molten third metal in the mold is inthe molten state for less than 75 seconds.
 77. The method according toclaim 75 wherein the molten third metal in the mold is in the moltenstate for less than 60 seconds.
 78. The method according to claim 75comprising two portions for securing respectively an insert, and two ofthe crystalline ceramic comprising reinforcement inserts positionedrespectively in the portions for securing respectively an insert. 79.The method according to claim 75 wherein the first metal is an aluminumalloy and wherein the third metal is an aluminum alloy.
 80. The methodaccording to claim 75 wherein the first metal is a 6000 series aluminumalloy, and wherein the third metal is one of a 300 or 400 seriesaluminum alloy.
 81. The method according to claim 75 wherein thecrystalline ceramic comprising reinforcement insert comprising porous,sintered ceramic oxide material and substantially continuous ceramicoxide fibers having lengths of at least 5 cm, the porous, sinteredceramic oxide material securing the substantially continuous ceramicoxide fibers in place, wherein the porous, sintered ceramic oxidematerial extends along at least a portion of the length of thesubstantially continuous fibers.
 82. The method according to claim 75wherein the metal matrix composite article is a brake caliper.
 83. Amethod of making a metal matrix composite article, the methodcomprising: positioning an insert holder that includes a metalcomprising reinforcement insert, the insert holder including at leastone portion for securing at least one insert, the insert holdercomprising a first metal selected from the group consisting of aluminum,alloys thereof, and combinations thereof, the insert holder having anouter surface, Ni on the outer surface of the insert holder, the Nihaving an outer surface; and Ag on the outer surface of the Ni, the Aghaving a thickness of at least 8 micrometers, and the metal comprisingreinforcement insert being secured in the at least one portion forsecuring at least one insert; providing molten second metal selectedfrom the group consisting of aluminum, alloys thereof, and combinationsthereof into the mold; and cooling the molten second metal to provide ametal matrix composite article.
 84. The method according to claim 83wherein the molten second metal in the mold is in the molten state forless than 75 seconds.
 85. The method according to claim 83 wherein themolten second metal in the mold is in the molten state for less than 60seconds.
 86. The method according to claim 83 wherein the metal matrixcomposite article is a brake caliper.
 87. A method of making a metalmatrix composite article, the method comprising: positioning an insertholder that includes a crystalline ceramic comprising reinforcementinsert, the insert holder including at least one portion for securing atleast one insert, the insert holder comprising a first metal selectedfrom the group consisting of aluminum, alloys thereof, and combinationsthereof, the insert holder having an outer surface, Ni on the outersurface of the insert holder, the Ni having an outer surface; and Ag onthe outer surface of the Ni, the Ag having a thickness of at least 8micrometers; providing molten second metal selected from the groupconsisting of aluminum, alloys thereof, and combinations thereof intothe mold; and cooling the molten second metal to provide a metal matrixcomposite article.
 88. The method according to claim 87 wherein themolten second metal in the mold is in the molten state for less than 75seconds.
 89. The method according to claim 87 wherein the molten secondmetal in the mold is in the molten state for less than 60 seconds. 90.The method according to claim 87 wherein the metal matrix compositearticle is a brake caliper.
 91. A method of making a metal matrixcomposite article, the method comprising: positioning an insert holderthat includes an insert in a mold, the insert holder including at leastone portion for securing at least one insert, the insert holdercomprising a first metal selected from the group consisting of aluminum,alloys thereof, and combinations thereof, the insert holder having anouter surface, and a second metal on the outer surface of the firstmetal, the second metal having a positive Gibbs oxidation free energyabove at least 200° C., the insert being secured in the at least oneportion for securing at least one insert and comprising substantiallycontinuous ceramic oxide fibers and third metal selected from the groupconsisting of aluminum, alloys thereof, and combinations thereof,wherein the third metal secures the substantially continuous ceramicoxide fibers in place, and wherein the third metal extends along atleast a portion of the length of the substantially continuous ceramicoxide fibers, the third metal having an outer surface; and a fourthmetal on the outer surface of the third metal, the fourth metal having apositive Gibbs oxidation free energy above at least 200° C., and thefourth metal having a thickness of at least 8 micrometers; providingmolten fifth metal selected from the group consisting of aluminum,alloys thereof, and combinations thereof into the mold; and cooling themolten fifth metal to provide a metal matrix composite article.
 92. Themethod according to claim 91 wherein the molten fifth metal in the moldis in the molten state for less than 75 seconds.
 93. The methodaccording to claim 91 wherein the molten fifth metal in the mold is inthe molten state for less than 60 seconds.
 94. The method according toclaim 91 comprising two portions for securing respectively an insert,and two of the inserts positioned respectively in the portions forsecuring respectively an insert.
 95. The method according to claim 91wherein the first metal is an aluminum alloy, wherein the third metal isan aluminum alloy, and wherein the fifth metal is an aluminum alloy. 96.The method according to claim 91 wherein the first metal is a 6000series aluminum alloy, wherein the third metal is a 200 series aluminumalloy, and wherein the fifth metal is one of a 300 or 400 seriesaluminum alloy.
 96. The method according to claim 91 wherein the metalmatrix composite article is a brake caliper.
 97. A method of making ametal matrix composite article, the method comprising: positioning aninsert holder that includes an insert in a mold, the insert holderincluding at least one portion for securing at least one insert, theinsert holder comprising a first metal selected from the groupconsisting of aluminum, alloys thereof, and combinations thereof, theinsert holder having an outer surface, the insert being secured in theat least one portion for securing at least one insert and comprisingsubstantially continuous ceramic oxide fibers and second metal selectedfrom the group consisting of aluminum, alloys thereof, and combinationsthereof, wherein the second metal secures the substantially continuousceramic oxide fibers in place, and wherein the second metal extendsalong at least a portion of the length of the substantially continuousceramic oxide fibers, the insert holder and the insert collectivelyhaving an outer surface, and a third metal on the outer surface, thethird metal having a positive Gibbs oxidation free energy above at least200° C., and the third metal having a thickness of at least 8micrometers; providing molten fourth metal selected from the groupconsisting of aluminum, alloys thereof, and combinations thereof intothe mold; and cooling the molten fourth metal to provide a metal matrixcomposite article.
 98. The method according to claim 97 wherein themolten fourth metal in the mold is in the molten state for less than 75seconds.
 99. The method according to claim 97 wherein the molten fourthmetal in the mold is in the molten state for less than 60 seconds. 100.The method according to claim 97 comprising two portions for securingrespectively an insert, and two of the inserts positioned respectivelyin the portions for securing respectively an insert.
 101. The methodaccording to claim 97 wherein the first metal is an aluminum alloy,wherein the second metal is an aluminum alloy, and wherein the fourthmetal is an aluminum alloy.
 102. The method according to claim 97wherein the first metal is a 6000 series aluminum alloy, wherein thesecond metal is a 200 series aluminum alloy, and wherein the fourthmetal is one of a 300 or 400 series aluminum alloy.
 103. The methodaccording to claim 97 wherein the metal matrix composite article is abrake caliper.
 104. A method of making a metal matrix composite article,the method comprising: positioning an insert holder that includes aninsert in a mold, the insert holder including at least one portion forsecuring at least one insert, the insert holder comprising a first metalselected from the group consisting of aluminum, alloys thereof, andcombinations thereof, the insert holder having an outer surface, Ni onthe outer surface of the insert holder, the Ni having an outer surface;and Ag on the outer surface of the Ni, the insert being secured in theat least one portion for securing at least one insert and comprisingsubstantially continuous ceramic oxide fibers and second metal selectedfrom the group consisting of aluminum, alloys thereof, and combinationsthereof, wherein the second metal secures the substantially continuousceramic oxide fibers in place, and wherein the second metal extendsalong at least a portion of the length of the substantially continuousceramic oxide fibers, the second metal having an outer surface; and Nion the outer surface of the second metal, the Ni having an outersurface; and Ag on the outer surface of the Ni, the Ag having athickness of at least 8 micrometers; providing molten third metalselected from the group consisting of aluminum, alloys thereof, andcombinations thereof into the mold; and cooling the molten third metalto provide a metal matrix composite article.
 105. The method accordingto claim 104 wherein the molten third metal in the mold is in the moltenstate for less than 75 seconds.
 106. The method according to claim 104wherein the molten third metal in the mold is in the molten state forless than 60 seconds.
 107. The method according to claim 104 wherein themetal matrix composite article is a brake caliper.
 108. A method ofmaking a metal matrix composite article, the method comprising:positioning an insert holder that includes an insert in a mold, theinsert holder including at least one portion for securing at least oneinsert, the insert holder comprising a first metal selected from thegroup consisting of aluminum, alloys thereof, and combinations thereof,the insert holder having an outer surface, the insert being secured inthe at least one portion for securing at least one insert and comprisingsubstantially continuous ceramic oxide fibers and second metal selectedfrom the group consisting of aluminum, alloys thereof, and combinationsthereof, wherein the second metal secures the substantially continuousceramic oxide fibers in place, and wherein the second metal extendsalong at least a portion of the length of the substantially continuousceramic oxide fibers, the insert holder and the insert collectivelyhaving an outer surface, Ni on the outer surface of the metal, the Nihaving an outer surface of the insert holder, and Ag on the outersurface of the Ni; providing molten third metal selected from the groupconsisting of aluminum, alloys thereof, and combinations thereof intothe mold; and cooling the molten third metal to provide a metal matrixcomposite article.
 109. The method according to claim 108 wherein themolten third metal in the mold is in the molten state for less than 75seconds.
 110. The method according to claim 108 wherein the molten thirdmetal in the mold is in the molten state for less than 60 seconds. 111.The method according to claim 108 wherein the metal matrix compositearticle is a brake caliper.